Misplaced Pages

#657342

108-630: An advisory speed limit is a speed recommendation by a governing body, used when it may be non-obvious to the driver that the safe speed is below the legal speed . It is a posting which either approximates the Basic Speed Law or rule (and is subject to enforcement as such) or is based on a maximum g-force exerted at a specific speed. Advisory speed limits are often set in areas with many pedestrians , such as in city centres and outside schools, and on difficult stretches of roads, such as on tight corners or through roadworks . While travelling above

216-496: A i " for a passenger vehicle from a stop up to 20 mph is about 0.15g, with more than 0.3g being difficult to exceed. The distance " d i " is the sum of the measured limit line setback distance—which is typically regulated by a Manual on Uniform Traffic Control Devices , at often between 4 and 30 feet in the United States —and the crosswalk , parking lane , and road shoulder width. A vehicle accelerating from

324-400: A two-second rule or three-second rule. See Table of 2-second following distances In the fifth case, critical speed V cs applies when road curvature is the factor limiting safe speed. A vehicle which exceeds this speed will slide out of its lane. Critical speed is a function of curve radius r , superelevation or banking e , and friction coefficient μ ; the constant g again

432-783: A citable driving offense, thus burdening an offending driver to rebut a presumption of negligence . States with such explicit ACDA standard of care provisions include: Iowa, Michigan, Ohio, Oklahoma, Pennsylvania, and Texas. States which apply the principle by statute to watercraft on navigable waterways include all 174 member states of the International Maritime Organization , notwithstanding membership: Great Britain and its common law inheriting Commonwealth of Nations , The United States, Florida, Hawaii, Illinois, Louisiana, Michigan, Montana, Oregon, Texas, and West Virginia. Most state-issued and some Canadian driver handbooks instruct or mention

540-446: A close vehicle in front. This maximum velocity is denoted by the case variable V A C D A s {\displaystyle V_{ACDA_{s}}} , the friction coefficient is symbolized by μ {\displaystyle \mu } —and itself a function of the tire type and road conditions , the distance d A C D A s {\displaystyle d_{ACDA_{s}}}

648-412: A driver happened to hit, could not have known, but had a concurrent duty to avoid. Furthermore, modern knowledge of human factors has revealed physiological limitations—such as the subtended angular velocity detection threshold (SAVT)—which may make it difficult, and in some circumstance impossible, for other drivers to always comply with right-of-way statutes by staying clear of roadway. As with

756-409: A driver on an uncontrolled through street has a duty to slow down in crossing an intersection and permit controlled drivers to be able pass through the intersection without danger of collision. The driver on the through street must anticipate and hence not approach at an unsafe speed which would prevent another driver from being able to enter while traffic was some distance away, or would be unsafe to

864-453: A driver who has already established control of the intersection under a prudent acceleration a i , from a stop at a limit line a distance d sl away. The pedantic fourth case applies when the dynamic ACDA "following distance" ( d ACDA d ) is less than the static ACDA "line-of-sight" distance ( d ACDA s ). A classic instance of this occurs when, from a visibility perspective, it would be safe to drive much faster were it not for

972-465: A foreseeable dynamic hazard—such as to maintain a distance as to be able to safely swerve around a bicyclist should he succumb to a fall—without requiring a full stop beforehand, if doing so could be exercised with due care towards surrounding traffic. Quantitatively this distance is a function of the appropriate time gap and the operating speed: d ACDA =t gap ⋅ v . The assured clear distance ahead rule, rather than being subject to exceptions,

1080-472: A forest with many trees which all eventually fell. In this specific regard, jurisdictions which grant drivers the liberty to be fools from their own folly, are also condoning the collateral damage and life loss which is expected to occur. Moreover, modern life-entrusting consumers of driving services and driverless cars who suffer such caused injury are left without legal remedy for foreseeable outcome of imprudent speed; this in-turn unnecessarily transfers

1188-442: A hazard. Collisions generally only occur within one's assured clear distance ahead which are "unavoidable" to them such that they have zero comparative negligence including legal acts of god and abrupt unforeseeably wanton negligence by another party. Hazards which penetrate one's proximate edge of clear visibility and compromise their ACDA generally require evasive action. Drivers need not and are not required to precisely determine

SECTION 10

#1732766075658

1296-465: A higher safe speed than human driven vehicles for a given ACDA where computer perception-reaction times are nearly instantaneous. The Assured Clear Distance Ahead can be subjective to the baseline estimate of a reasonable person or be predetermined by law. For example, whether one should have reasonably foreseen that a road was not assuredly clear past 75–100 meters because of tractors or livestock which commonly emerge from encroaching blinding vegetation

1404-734: A message, whereas newer models may be reprogrammed remotely via a wired or wireless network or cellphone connection. A complete message on a panel generally includes a problem statement indicating incident, roadwork, stalled vehicle etc.; a location statement indicating where the incident is located; an effect statement indicating lane closure, delay, etc. and an action statement giving suggestion what to do traffic conditions ahead. These signs are also used for Amber alert messages, and in some states, Silver and Blue Alert messages. In some places, VMSes are set up with permanent, semi-static displays indicating predicted travel times to important traffic destinations such as major cities or interchanges along

1512-407: A moose or a luxury car. Furthermore, modern times still provide no legal remedies for Darwinian misfortune upon the entire class of unwarnable accidents where drivers and their passengers would not have collided into the likes of a moose, livestock, fallen tree, rock, jetsam, horse-drawn vehicle, stalled vehicle, school bus, garbage truck, mail carrier, snowplow, washout, snow drift, or slid off

1620-452: A result of this uncorrected vagueness, group behavior can often be in opposition to safe speed and still be governing a hazardous posted speed limit. By federal law, posted speed limits are generally within 5 mph of the 85th-percentile speed of free-flowing traffic. Functionality, this amounts to citizens "voting" a street's speed limit with their gas pedal from the influence of groupshift . As people generally follow explicit rules all

1728-703: A road must be designed and maintained such that there is not a chance of obstruction in one's lane beyond the proximate edge of clear visibility. A road's vertical profile must be assured to have such a curvature as not to hide hazards close behind its crests. Discretion for drivers and pedestrians to enter onto a potentially occupied lane from a side street must be assuredly eliminated such as with fences, merge lanes, or signalized access. There must also be an assurance of no opportunity for animals and debris to enter from side lots, and that there are continuous multi-hourly maintenance patrols performed. Furthermore, such road sections must be distinguished from other roads so that

1836-510: A road's inferred design speed. Collision liability has historically benefited the law profession by being cloaked as a mixture of fact and law, but with EDR's precisely preserving "a state of facts" often repeated with differing trial outcomes, collisions are less a question of fact, but of law. Electronic access to precise EDR data and rulings with new ideological modeling tools, can now expose judges as consistent political advocates for differing special road user interests. Furthermore,

1944-525: A roadway at over 30 mph (48 km/h). Wildlife will frequently transit across a road before a full stop is necessary, however collisions with large game are foreseeably lethal, and a driver generally has a duty not to harm his or her passengers. The foreseeable intercept speed or defectively designed horizontal sight distance may vary "reasonably" with judicial discretion . See Table of safe speed versus horizontal line-of-sight This third case regards safe speed around un-signalized intersections where

2052-405: A slower-moving vehicle ahead. As such, the dynamic ACDA is governing the basic speed rule, because in maintaining this distance, one cannot drive at a faster speed than that matching the forward vehicle. The "time gap" t g or "time cushion" is the time required to travel the dynamic ACDA or "following distance" at the operating speed . Circumstances depending, this cushion might be manifested as

2160-411: A speed above which no reasonable minds might differ as to whether it is unsafe or that one could come to a stop within the full distance ahead. Drivers and law enforcement alike can apply elementary level arithmetic towards a rule of thumb to estimate minimal stopping distance in terms of how many seconds of travel ahead at their current speed. For speed " v " in miles per hour, this rule of thumb

2268-589: A speed at which lateral g-forces will not exceed 0.22g to fall well within the minimum suggested static rollover threshold of 0.35g for non-dangerous goods. The Richtgeschwindigkeit ( pronounced [ˈʁɪçtɡəˌʃvɪndɪçkaɪ̯t] , German for Advisory or Suggested Speed of Travel) is a legal term in Germany describing the advisory speed limit for roads without a mandatory speed limit . Autobahns have an advisory speed limit of 130 kilometres per hour (81 mph) on non-signposted sections. Exceeding

SECTION 20

#1732766075658

2376-408: A stop travels this distance in time t i = √ 2d i ⁄ a i while through traffic travels a distance equal to their speed multiplied by that time. The time t pc , for the stopped motorist, is the sum of perception time and the time required to actuate an automatic transmission or shift to first gear which is usually between 1 ⁄ 2 to one second. Horizontal clearance

2484-406: A strict standard of care, delegation of such standard to a jury assumes the representativeness heuristic for twelve people to determine ordinary care representative of everyone while ignoring its insensitivity to sample size , which of course when applied to multiple cases involving identical situational circumstances results in many verdicts with opposing extreme views, which works against

2592-574: A substantive portion of the ACDA liability space into act of god , government claims , strict liability , or other findings from legal fiction which the justice system generally abhors. What modern times are changing is that one may assure the distance is clear ahead virtually through the Internet of Things , as smart cars connect to get information from smart highways or pass what they see ahead or measure to traffic behind. A fundamental corollary of

2700-418: A trajectory or firing solution in order to hit a target with repeated accuracy. During the earliest stages of learning how to drive , one develops a memory of when to start braking (how long it takes) from various speeds in order to stop at the limit line. While there may be a degree of variance of such skill in seasoned drivers, they generally do not have the discretion in engaging in a behavior such as driving

2808-515: Is a common problem in the winter), and of slow or stopped traffic. Message Signs were deployed in Ontario during the 1990s and are now being upgraded on 400-series highways as well as two pilot secondary highways in northeastern Ontario. Early variable message signs included static signs with words that would illuminate (often using neon tubing) indicating the type of incident that occurred, or signs that used rotating prisms ( trilons ) to change

2916-595: Is a more recent introduction, where maintenance on the sign is performed from the inside of the sign. A key advantage of the walk-in form factor is that lane closures are generally not required to perform maintenance on the sign. Most of the largest VMS units installed today are walk-in units, and are typically installed overhead on freeways. The NJ Turnpike Authority counts five unique types of variable message signs under its jurisdiction, at least one of which has been replaced by newer signs. They are: Early models required an operator to be physically present when programming

3024-407: Is a precautionary trivial burden required to avert the great probable gravity of precious life loss and momentous damage. Satisfying the ACDA rule is necessary but not sufficient to comply with the more generalized basic speed law , and accordingly, it may be used as both a layman's criterion and judicial test for courts to use in determining if a particular speed is negligent, but not to prove it

3132-531: Is a prolific source of accidents. In the United States , there is no explicit road marking promising clear distance beyond line of sight in the Manual on Uniform Traffic Control Devices , although there are signs communicating " limited sight distance ", " hill blocks view ", " crossroad ahead ", and " freeway ends ". A partial solution to this challenge is to remove driver discretion in determining whether

3240-803: Is a standard with descriptive mathematics, much of which are used in reverse by road engineers when designing or re-engineering roads to a speed criteria—for which its users were expected to follow. The range of visibility of which is the de facto ACDA, is usually that distance before which an ordinary person can see small hazards—such as a traffic cone or buoy —with 20/20 vision . This distance may be attenuated by specific conditions such as atmospheric opacity , blinding glare , darkness, road design , and adjacent environmental hazards including civil and recreational activities, horse-drawn vehicle, ridden animal, livestock, deer, crossing traffic, and parked cars . The ACDA may also be somewhat attenuated on roads with lower functional classification . This

3348-466: Is an ever important foundational rule in today's complex driving environment. Because there are now protected classes of roadway users—such as a school bus , mail carrier , emergency vehicle , horse-drawn vehicle , agricultural machinery , street sweeper , disabled vehicle , cyclist , and pedestrian —as well as natural hazards which may occupy or obstruct the roadway beyond the edge of visibility, negligence may not depend ex post facto on what

Advisory speed limit - Misplaced Pages Continue

3456-411: Is as follows: If this distance is greater than the ACDA, they need to decelerate. While most experienced drivers develop a broad intuition required by everyday braking, this rule of thumb can still benefit some to recalibrate expectations for rare hard braking, particularly from high speeds. Additional simple corrections can be made to compensate for the environment and driving ability. Read more about

3564-625: Is because the probability of spontaneous traffic increases proportionally to the density of road access points, and this density reduces the distance a person exercising ordinary care can be assured that a road will be clear; such reduction in the ACDA is readily apparent from the conditions, even when a specific access point or the traffic thereon is not. Furthermore, even though a through-driver may typically presume all traffic will stay assuredly clear when required by law, such driver may not take such presumption when circumstances provide actual knowledge under ordinary care that such traffic cannot obey

3672-514: Is forbidden by such hazard, and any legal expectation to the contrary would implicate violating the vagueness doctrine of the US Constitution . It is the duty of the through-driver to decelerate and apply the ACDA principle specifically to the intersection. See Table of detection thresholds . When approaching an un-signalized intersection controlled by a stop sign , the assured clear distance ahead is: Normal acceleration "

3780-485: Is measured from the edge of the traveled way to the bottom of the nearest object, tree trunk or shrub foliage mass face, plant setback, or mature growth. Horizontal sight distance is not to be confused with the clear recovery zone which provides hazardous vegetation set-back to allow errant vehicles to regain control, and is exclusive to a mowed and limbed-up forest which can allow adequate sight distance, but unsafe recovery. The height and lateral distance of plants restrict

3888-490: Is not defined by the Vienna Convention on Road Signs and Signals , and is therefore not standardised internationally. The United States uses a small yellow sign under the main warning sign, as well as a standalone variation on the standard speed limit sign, with a yellow background instead of a white one, the words "speed limit" omitted and an additional panel stating the type of hazard ahead. Though they list speeds,

3996-825: Is not really intended to apply beyond situations in which a vigilant ordinarily prudent person could or should anticipate. A common way to violate the dynamic ACDA is by tailgating . The most accurate way to determine the ACDA is to directly measure it. Whereas this is impractical, sight distance formulas can be used with less direct measurements as rough baseline estimates. The empirical assured clear distance ahead calculated with computer vision , range finding , traction control , and GIS , such as by properly programming computer hardware used in autonomous cars , can be recorded to later produce or color baseline ACDA and safe speed maps for accident investigation, traffic engineering, and show disparities between safe speed and 85th percentile "operating" speed. Self-driving cars may have

4104-405: Is on occasion dependent on societal experience within the locale. In certain urban environments, a straight, traffic-less, through-street may not necessarily be assuredly clear past the entrance of the nearest visually obstructed intersection as law. Within the assured clear distance ahead, there is certainty that travel will be free from obstruction which is exclusive of a failure to appreciate

4212-431: Is otherwise reached. Steering control is independent from any concept of clear distance ahead. If a vehicle cannot be controlled so as to safely remain within its lane above a certain speed and circumstance, then it is irrelevant how assuredly clear the distance is ahead. Using the example of the previous case, the safe speed on a curve may be such that a driver experiences a lateral acceleration of less than 0.3g despite that

4320-446: Is performed by lifting the sign open from the front. Most smaller VMS are of the front access form factor, and are typically installed today on major arterials. The rear access form factor is similar to the front access form factor, except that maintenance is performed from the rear of the sign, and are commonly used for medium-sized dynamic message signs installed along the roadside of freeways (instead of overhead). The walk-in form factor

4428-468: Is prohibited, and people of ordinary intelligence can apply their braking experience or the seconds of distance to stop rule to the distance they can see; once one is allowed to cruise-on without control beyond the edge of visibility, there is little consensus on what arbitrary speed is unsafe, or what to assume of the vague conditions there-past. To be able to guarantee "assurance" beyond proximate edge of clear visibility, in doing so exempting ACDA duty,

Advisory speed limit - Misplaced Pages Continue

4536-473: Is safe. As a spatial standard of care , it also serves as required explicit and fair notice of prohibited conduct so unsafe speed laws are not void for vagueness . The concept has transcended into accident reconstruction and engineering. This distance is typically both determined and constrained by the proximate edge of clear visibility, but it may be attenuated to a margin of which beyond hazards may reasonably be expected to spontaneously appear. The rule

4644-410: Is than an accident which would not have occurred except for the action or inaction of some person or entity contrary to a duty such as the exercise of proper care was the result of negligence . The liability space from which one can recover is typically, themselves, other parties, or nobody. Jurisdictional exceptions permitting one to legally take "assurance" that the distance will be clear beyond

4752-452: Is the acceleration of gravity. However, most motorists will not tolerate a lateral acceleration exceeding 0.3g ( μ  = 0.3) above which many will panic. Hence, critical speed may not resemble loss of control speed. Attenuated "side" friction coefficients are often used for computing critical speed. The formula is frequently approximated without the denominator for low angle banking which may be suitable for nearly all situations except

4860-485: Is the distance ahead of any terrestrial locomotive device such as a land vehicle , typically an automobile , or watercraft , within which they should be able to bring the device to a halt. It is one of the most fundamental principles governing ordinary care and the duty of care for all methods of conveyance, and is frequently used to determine if a driver is in proper control and is a nearly universally implicit consideration in vehicular accident liability. The rule

4968-751: Is the maximum speed at which a vehicle can come to a full stop before an object, with speed V i , can intercept after having emerged and traveled across the horizontal sight distance "d hsd ". Urban and residential areas have horizontal sight distances that tend to be closely obstructed by parked cars, utility poles, street furnishing, fencing, signage, and landscaping, but have slower intercepting speeds of children, pedestrians, backing cars, and domestic animals. These interceptors combined with dense usage results in collisions that are more probable and much more likely to inflict harm to an outside human life. In rural areas, swift-moving spooked wildlife such as deer , elk , moose , and antelope are more likely to intercept

5076-418: Is the specific spatial case of the common law basic speed rule , and an application of volenti non fit injuria . The two-second rule may be the limiting factor governing the ACDA, when the speed of forward traffic is what limits the basic safe speed, and a primary hazard of collision could result from following any closer. As the original common law driving rule preceding statutized traffic law , it

5184-422: Is the static ACDA, the constant g {\displaystyle g} is the acceleration of gravity , and interval t p r t {\displaystyle t_{prt}} is the perception-reaction time —usually between 1.0 and 2.5 seconds. See Table of safe speed versus forward line-of-sight The second case describes the relationship of horizontal sight distance on safe speed. It

5292-417: Is well known that people instead resolve such challenges by attribute substitution , which in this case can mean simply emulating the behaviors of others. In accord with the cultural theory of risk , indeed a substantial part of a driver's risk perception comes from comparing their contemplated conduct to the behavior of others; this includes the safeness of a given speed, notwithstanding the actual risk. As

5400-532: The Autobahn-Richtgeschwindigkeits-Verordnung (Directive on Reference Speed on Motorways), introduced in 1974, recommends a speed of no more than 130 km/h (81 mph) for autobahns and similar roads, whose lanes are separated by a median or which have at least two lanes per direction, provided there are no traffic signs posting a lower speed limit. Until 31 August 2009, a different reference speed could be posted by

5508-609: The Richtgeschwindigkeit ("reference speed") in Germany is valid for the whole autobahn network (but can be overruled by speed limits in particular sections or for special reasons like weather conditions or roadworks), while the United States and the United Kingdom only give advisory speed limits for hazards such as bends. Use of advisory speed limits varies by locale, but they are generally used to reduce speed along short stretches of dangerous road, such as on

SECTION 50

#1732766075658

5616-539: The Garden State Parkway ) with more flexible electronic signs between 2010 and 2016. The current VMS systems are largely deployed on freeways , trunk highways, or in work zones. On the interchange of I-5 and SR 120 in San Joaquin County , California, an automated visibility and speed warning system was installed in 1996 to warn traffic of reduced visibility due to fog (where tule fog

5724-519: The Seconds of Distance to Stop Rule . The ACDA distances are a principal component to be evaluated in the determination of the maximum safe speed (V BSL ) under the basic speed law, without which the maximum safe speed cannot be determined. As mathematical statements are more precise than verbal statements alone, the relation of the ACDA as a subset of the basic speed rule for land based vehicles may be objectively quantified as follows: The value of

5832-540: The Transportation Research Board found advisory speed limits through roadworks being consistently flouted by motorists, while an investigation by Manchester Evening News found that almost all buses in Manchester city centre exceeded the local 10 miles per hour (16 km/h) advisory speed limit; some by as much as 30 miles per hour (48 km/h). The signage for advisory speed limits

5940-477: The calculus of negligence because speed is an inherent factor in vehicular accidents which are a leading cause of priceless life loss and lawsuits, and the burden of a precautions speed is radically lower than the former. The assumption of risk resulting from the unsafe activity of driving faster than one can stop within one's vision, does not depend ex post facto on what you happened to hit, for which by nature you could not have known; it could have been

6048-498: The inferred design speed . In some cases, police focused on driving while "influenced", pull over slower quartile sober night-time drivers moving no faster than they can stop within the radius of their headlights; this discourages adjusting speed downward from anything but the posted "maximum speed" permitted by law—which is determined as previously described. It is often unsafe or illegal to drive in excess of 40–50 mph at night. A general principle in liability doctrine

6156-477: The maximum posted speed limit at night, often in violation of the ACDA rule and this shows up in accident data. As a corollary to the rule that drivers generally must not pose an "immediate hazard" upon where or when they cannot assure such distance ahead is clear, it follows that others may presume that no vehicle is posing an "immediate hazard" from beyond where they can see with proper lookout. Where there are cross roads or side roads with view obstructions,

6264-509: The 1950s on the New Jersey Turnpike . The road's signs of that period, and up to around 2012, were capable of displaying a few messages in neon, all oriented around warning drivers to slow down: "REDUCE SPEED", followed by a warning of either construction, accident, congestion, ice, snow, or fog at a certain distance ahead. The New Jersey Turnpike Authority replaced those signs (along with 1990s-vintage dot-matrix VMS systems along

6372-614: The ACDA duty of which instills the necessary room to survive uninjured from such foreseeable and excusable error while adding redundancy in the responsibility to avoid a collision; mere unilateral duties laid down to assure the safety of others tend to result in hazardous risk compensation by those unfettered parties resulting in a moral hazard . Allowing one to drive faster than their vision permits them to safely stop, results in there being no core standard of care regarding safe speed making unsafe speed laws void for vagueness . The ACDA minimum standard gives fair notice of what conduct

6480-508: The ACDA is extended beyond line of sight, by explicitly designating this law change to certain marked high functional classification roadways having meet strict engineering criteria. The ACDA rule is analogous to aviation visual flight rules , and its discussed exception—allowed only in a well regulated control zone—is analogous to instrument flight rules . Unlike both visual and instrumental flight rules, where federal and international administrative law applies seamlessly and uniformly across

6588-638: The ACDA rule as required care or safe practice. Explicit ACDA statutes and regulations, especially those of which create a citable driving or maritime offense, are aimed at preventing harm that could result from potentially negligent behavior—whereas the slightly more obscure common law ACDA doctrine is most easily invoked to remedy actual damages that have already occurred as a result of such negligence. Unsafe speed statutes are immune from being void for vagueness when they contain explicit ACDA clauses. Explicit and implicit ACDA rules govern millions of North American drivers. Not all jurisdictions have applied

SECTION 60

#1732766075658

6696-517: The ACDA rule is that technology, expectations, and desires may modernize, but the laws of physics can not and do not. The deceleration coefficients and reactions times may change from conveyance by chariot , horse and buggy , internal combustion engine , electric motor , and by driverless car, but the equations governing stopping distances are immutable. Finally, where it is the policy of the law not to fault well intending diligent citizens for innocent mistakes, human life reaps continued benefit from

6804-470: The Australian design without the "km/h" lettering). Ireland and the United Kingdom currently use an oblong white rectangle, the latter with black lettering stating "Max Speed". In both countries it may not be used on its own – it must be used in conjunction with the appropriate warning sign. Assured Clear Distance Ahead#Safe speed In legal terminology, the assured clear distance ahead ( ACDA )

6912-562: The Federal Highway Administration to strongly discourage signs with "obscure meanings, references to pop culture" or humor. Truck-mounted VMSes (also called Portable Changeable Message Signs or PCMS) are sometimes dispatched by highway agencies such as Caltrans to warn traffic of incidents such as accidents in areas where permanent VMSes are not available or near enough as a preventive measure for reducing secondary accidents. They are often deployed in pairs so that

7020-424: The United States advisory speed signs are classified as warning signs, not regulatory signs, as primary speed signs are. Australia uses a similar design as the United States in spite of regulatory speed limit signs being quite different. Germany used a square sign with a blue background and white lettering, similar to the minimum speed limit sign, and New Zealand uses a yellow background with black lettering (similar to

7128-409: The ability to display colored text and graphics. Dot-matrix variable message signs are divided into three subgroups: character matrix, row matrix, and full matrix. In a character matrix VMS, each character is given its own matrix with equal horizontal spacing between them, typically with two or three rows of characters. In a full matrix VMS, the entire sign is a single large dot matrix display, allowing

7236-594: The advised speed is not a criminal offense, but may result in greater liability in the case of a collision due to an increased danger of operating the vehicle. There are multiple court cases where another car was recklessly cutting into the left lane but partial liability was assigned to the speeding driver nevertheless ( Bundesgerichtshof , 17 March 1992, VI ZR 62/91: cut in without blinking, speeding at 150–180 km/h, 25% liability; OLG Koblenz , 14 October 2013, Az. 12 U 313/13: cut in from ramp directly across two lanes, speeding at 200 km/h, 40% liability) In Germany,

7344-410: The advisory speed limit is not illegal per se , it may be negligence per se and liability for any collisions that occur as a result of traveling above the limit can be placed partially or entirely on the person exceeding the advisory speed limit. Signposting of advisory speed limits varies from country to country; Australia makes extensive use of advisory speed limits across its highway networks while

7452-433: The assured clear distance terminates at the closest path of potential users of the roadway until there is such a view which assures the intersection will remain clear. In such situations, approach speed must be reduced in preparation for entering or crossing a road or intersection or the unmarked pedestrian crosswalks and bike paths they create because of potential hazards. This jurisprudence arises in-part because of

7560-418: The conditions along the road. See reference V BSL derivations for basic physics explanation. For the top case, the maximum speed is governed by the assured clear "line-of-sight", as when the "following distance" aft of forward traffic and "steering control" are both adequate. Common examples include when there is no vehicle to be viewed, or when there is a haze or fog that would prevent visualizing

7668-436: The conditions. The speeds at which most people drive can only be a very rough guide to safe speed, and an illegal or negligent custom or practice is not in itself excusable. Safe speed approximates the inferred design speed adjusted for environmental alterations and vehicle and person specific factors when V ACDA s is the limiting factor. The Solomon curve concept can create an approach-avoidance conflict within

7776-539: The criminal blood alcohol threshold below levels for which the risk is statistically marginal, the tolerance for speeding—of which each speed unit increment carries an equatable risk relative to BAC —remains relatively neglected. Speed is responsible for more crashes and economic loss than is alcohol. The discrepancy may be partly explained by powerful special interest groups that are lobbying against drunk driving and for loser speed regulation. Variable-message sign VMS systems were deployed at least as early as

7884-521: The details. By the late 1920s, the term "assured clear distance ahead" came into widespread use as the identity of a standard of care element in choosing safe speed, with differing jurisdictions adopting the language to carry its same effects. Much of the earliest published record naturally pertains to high stakes wrecks among vessels or vehicles as defined in those times, though the obvious principle applies to chariots and might in fact be time immemorial . Horses may still be expected to use

7992-428: The display of different fonts and graphics. A row matrix VMS is a hybrid of the two types, divided into two or three rows like a character matrix display, except each row is a single long dot matrix display instead of being split per character horizontally. Overhead variable message signs are today available in three form factors: front access, rear access, and walk-in. In a front access variable message sign, maintenance

8100-459: The distance to remain clear beyond line of sight would ultimately be transferred to its taxpayers. This only generally occurs when governments have been tasked by constituents or their courts to take the responsibly to design and maintain roadways that "assure" the distance will be clear beyond the proximate edge of clear visibility. Pressures to make such changes may arise from cultural normalization of deviance and unnecessary risk, misunderstanding

8208-431: The driver could clearly and immediately know when he or she may or may not take such extended "assurance". Few roads might meet these requirements except some of the highest functional classification controlled-access highways such as freeways and autobahns . Even if such criteria are met, the law must also exempt driver liability for maintaining clear distance ahead. In most democracies, such liability for failures of

8316-416: The driver who wishes neither to drive faster than is lawful and the conditions allow nor have an unsafe speed discrepancy between other vehicles on the road; it is never legal to go faster than the speed limit, and unilaterally reducing the risk of the latter can lead to a mass crash caused by the former. Many people are challenged by the concept of unsafe speed because they find it vague and arbitrary. It

8424-496: The genesis of most legal doctrine governing problems which precede a legislative solution, the ACDA principle generally originates to decisional precedent by high courts which reasoned general common sense rules of conduct of which naturally follow from the repetitive process of determining specific culpability. Legislation often subsequently followed which either superfluously codified and endorsed or revised these principles, of which courts would in turn continue to flesh out

8532-443: The horizontal sight distance in time to collide, however this says nothing of whether the vehicle can stop by the end of this type of assured clear distance. Equating this distance to the total stopping distance and solving for speed yields one's maximum safe speed as purely dictated by the horizontal sight distance. The ACDA may also be dynamic as to the moving distance past which a motorist can be assured to be able to stay clear of

8640-406: The horizontal sight distance, at times obscuring wildlife which may be spooked by an approaching vehicle and run across the road to escape with their herd . This principle also applies to approaching vehicles and pedestrians at uncontrolled intersections and to a lesser degree by un-signalized intersections controlled by a yield sign . Horizontal sight distance " d hsd " affects the ACDA because

8748-532: The inclusion of a red ring surround, effectively changing them from advance hazard warnings into standard, mandatory speed-limit signs. As local councils require consent from the Department for Transport before changing speed limits, some use advisory speed limits on roads that the DfT refuses to officially downgrade. The usefulness of advisory speed limits has been questioned by a number of studies: one group from

8856-438: The judiciary has explicitly established the state's ACDA law include Indiana, Iowa, Kansas, Louisiana, Michigan, New York, North Carolina, Ohio, Tennessee, Vermont, Wisconsin, and California. Many states have further passed statutes which require their courts to more inflexibly weigh the ACDA in their determination of reasonable speed or behavior. Such statutes do so in part by designating ACDA violations as

8964-460: The known difficulty in estimating the distance and velocity of an approaching vehicle, which is psychophysically explained by its small angular size and belated divergence from an asymptotically null rate of expansion, which is beyond the subtended angular velocity detection threshold (SAVT) limits of visual acuity by way of the Stevens' power law and Weber–Fechner law , until

9072-403: The law needs to be clear, precise, and uniform at a national level for the panoply of automobile manufacturers with the strict liability for their programming of law-abiding self-driving vehicles. It is foreseeable that two self-driving car makes can collide because their algorithm of the law letter is different; a resolvable issue that has been troubling human drivers for decades. The ACDA

9180-465: The law. During times of darkness, commercial vehicles can see ahead about 250 feet with low beams, and about 350–500 feet with high beams. This clear distance corresponds to a maximum safe speed of 52 mph and 65-81 mph respectively on dry pavement with good tires, which is attenuated further by convex and lateral road curvature ; safe speed is always dynamic. Non-commercial vehicles have even shorter lighting distances. Drivers commonly drive

9288-442: The maximum safe speed from real-time mathematical calculations of sight distances and stopping distances for their particular vehicle. Motor vehicle operators of average intelligence are constantly required to utilize their kinesthetic memory in all sorts of driving tasks including every time they brake to a full stop at a stop line in a panoply of conditions. Like throwing a softball, one does not have to mathematically calculate

9396-437: The message being displayed. These were later replaced by dot matrix displays typically using eggcrate , fiber optic , or flip-disc technology, which were capable of displaying a much wider range of messages than earlier static variable message signs. Since the late 1990s, the most common technology used in new installations for variable message signs are LED displays . In recent years, some newer LED variable message signs have

9504-539: The minimum static rollover threshold of 0.35g. In the United Kingdom, most speed limits imposed by variable-message signs are advisory, and there are no sanctions for drivers who exceed them; a notable exception being the Gatsometer -camera enforced, MIDAS and ATM variable limits on motorways such as the M25 , M42 and M6 . Crucially, the signs imposing these limits are distinct from regular, advisory VMS displays by

9612-698: The proximate edge of clear visibility and choose such a speed accordingly, transfers classic common law liability from that driver for his or her "blind" actions. This duty to assure clear distance ahead is inevitably transferred, as an externality to everybody or thing else who must instead warn the driver, such as the government, its road engineers, and maintainers. As it is generally probable and foreseeable that, chance will permit, and at some point there will be an obstruction beyond some driver's line of sight, such an entitlement challenges centuries of precedent in negligence doctrine in addition to posing difficult policy and engineering challenges. It also violates

9720-440: The purpose of the road functional classification system, underestimation of increased risk, and reclamation of commute time. One of the greatest difficulties created by such an extension of the ACDA is the frequency at which roads reduce their functional classification unbeknownst to drivers who continue unaware they have lost this extended "assurance" or do not understand the difference. Such nuance in applicable jurisdictions

9828-468: The range of his vision. In numerous jurisdictions, this rule has been incorporated in statutes which typically require that no person shall drive any motor vehicle in and upon any public road or highway at a greater speed than will permit him to bring it to a stop within the assured clear distance ahead." Decisional law usually settles the circumstances by which a portion of the roadway is assuredly clear without it being mentioned in statute. States where

9936-408: The road, were it not for their decisions to drive faster than dictated by the assured clear distance ahead. Regardless of what behavior an authority might encourage by fabricating new rights, it remains timeless that constituents cannot sue the wind for causing a wreck when it inevitably violates a "modern right to drive faster than permitted by the ACDA" by failing to warn them it knocked down a tree in

10044-403: The roadways, as well bicycles and automobiles. The former are a regular appearance in both urban areas and in the country , and are commonly exercised by commuters and Amish . Many roads are unchanged since the 1800s while controlled-access highways have been invented specifically for the automobile. "At common law a motorist is required to regulate his speed so that he can stop within

10152-402: The route of a highway. Typical messages provide the following information: The information comes from a variety of traffic monitoring and surveillance systems. It is expected that by providing real-time information on special events on the oncoming road, VMS can improve motorists' route selection, reduce travel time, mitigate the severity and duration of incidents and improve the performance of

10260-493: The rule uniformly, most often differing over exceptions for specific "sudden emergencies". There has been an increased interest in the ACDA codified as a universal standard of care that has been brought about by recent technological and social changes such as event data recorders , dashcams , self-driving cars , safe cities and multi-use movements, and a movement to reduce claims by speeders against governments for "dangerous conditions" when operating speeds exceed

10368-649: The second VMS truck can take over when the traffic queue overtakes the first truck, requiring the first truck to reposition further upstream from the queue, to be effective. An optional third truck, the team leader, may be utilized for driving by and monitoring the incident itself, traffic patterns and delay times, to make strategic decisions for minimizing delays—analogous to spotter planes used in fighting forest fires. Trailer-mounted variable-message signs are used to alter traffic patterns near work zones, and for traffic management for special events, natural disasters, and other temporary traffic patterns. The messages displayed on

10476-592: The sign can be programmed locally on the unit's control panel, or units equipped with a cellular modem can be programmed remotely via computer or phone. Most manufacturers produce trailers which comply with the National Transportation Communications for Intelligent Transportation System Protocol (NTCIP) which allows the portable trailer to be integrated with an intelligent transportation system . Trailer-mounted VMS can be equipped with radar, cameras, and other sensing devices as part of

10584-431: The states, the ACDA rule governing ground transportation is relatively variegated across states and judicial circuits . Primitive patchwork governance over a prominent interstate commercial subject , in a modern era where citizens quickly and more frequently travel father than ever before, creates problems for modern driverless cars which are programmed, distributed, sold, and traded at national levels. As opposed to

10692-798: The tight curves of an off-ramp or on a busy shopping street. The advisory speed limit when not posted is generally the same as the mandatory speed limit in ideal conditions. In Australia, if a person is involved in a single vehicle accident and the resulting investigation reveals that the driver was exceeding the Advisory Speed Limit displayed it can be a breach of the Insurance Cover Contract, resulting in no payout. Advisory speeds in corners are set out in AS (Australian Standard) 1742.2-2009 Manual of Uniform Traffic Control Devices, Part 2, appendix F. Corners are signed to indicate

10800-445: The tightest radius of highway onramps. The principle of critical speed is often applied to the problem of traffic calming , where curvature is both used to govern maximum road speed, and used in traffic circles as a device to force drivers to obey their duty to slow down when approaching an intersection. See Table of curvatures and critical speeds The bottom case is invoked when the maximum velocity for surface control V cl

10908-471: The time t i = ⁠ d hsd / V i ⁠ it takes for an intercepting object, animal, pedestrian, or vehicle with speed " V i " to transverse this distance after emerging from the proximate edge of lateral visibility affords a vehicle with speed " V " a clear distance of " V*t i ". Thus, the assured clear intercept distance " ACDA si " is: The faster one drives, the farther down-road an interceptor must be in order to be able to transverse

11016-429: The time of which they do not agree, it is often simply a jurisdiction's failure in their law to sufficiently quantify and disseminate fair notice of an explicit standard of care, such as the ACDA rule. Most DMV driver manuals teach the practice, but far fewer states explicitly back it up in their actual statutes and law enforcement. If drivers were mindful of the ACDA, the operating speed would by definition not exceed

11124-514: The traffic signs number 380 and 381, according to §42 of the German traffic code ( St raßen v erkehrs o rdnung, StVO), as seen above. As these traffic signs were only rarely used, they have been abolished, and will be fully removed by 31 October 2022. Advisory speeds are not legal speed limits. Advisory speeds end in 5 to avoid confusion with mandatory speed limits, which end in 0. The limits are established at 0.22g lateral g-force to fall well within

11232-864: The transportation network. * Do not enter the motorway when the red lamps are flashing in pairs from side to side. Increasingly, signs have been used to remind drivers to buckle seat belts ("Click it or ticket"), obey the speed limit, and stay off the road if impaired ("Drive sober or get pulled over"). In a federal study, a slight majority of drivers reported that public safety messages on dynamic message signs impacted their driving behaviors. The Ohio Department of Transportation began using humorous dynamic message signs in 2015, perplexing some drivers. Examples of humorous signs seen in New Jersey , Arizona , Texas , Pennsylvania , Delaware , Iowa , New York , Minnesota and Ohio include: In 2024, concerns that these messages were distracting drivers led

11340-456: The utility of the law by making it arbitrarily vague . A national uniformity standard which either administratively lays down the ACDA law as has been done for aircraft, or requires states to legislatively enact in order to receive federal DOT funding as has been done for the national legal drinking age, is a subject of debate for those who argue far more people die in cars than in aircraft. While group polarization towards safety has shifted

11448-523: The variable "e" is the sine of the angle of inclination of the road's slope . For a level road this value is zero, and for small angles it approximates the road's percent grade divided by one hundred. The maximum velocity permitted by the Assured Clear Distance Ahead is controlling of safe speed (V BSL ) for only the top and two cases. Safe speed may be greater or less than the actual legal speed limit depending upon

11556-509: The vehicle may be dangerously close; subjective constancy and the visual angle illusion may also play a role. Vehicles that are approaching an intersection from beyond the SAVT limit cannot be reliably distinguished between moving or parked, though they may be traveling at such an imprudent speed as to pose an immediate hazard. In this circumstance, it is impossible for the entering driver to have fair notice that his or her contemplated conduct

11664-681: The vehicle may not slide until it experiences 0.8g. Speed wobble , hydroplaning , roll center , fishtailing , jackknife tendencies, potholes , washboarding , frost heaving , and tire speed rating are other factors limiting V cl . Safe speed is the maximum speed permitted by the basic speed law and negligence doctrine. Safe speed is not the same as the 85 percentile operating speed used by traffic engineers in establishing speed zones. Fog, snow, or ice can create conditions where most people drive too fast, and chain reaction accidents in such conditions are examples of where large groups of drivers collided because they failed to reduce speed for

#657342