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81-637: The original 1.2-mile (1.9 km) deck truss bridge opened in 1962 to replace the last automotive ferry service in the San Francisco Bay Area . The 1962 bridge has seven 528-foot (161 m) spans and 138 feet (42 m) of vertical clearance, now carrying four lanes of southbound traffic, as well as a path for pedestrians and bicyclists. It was named the George Miller Jr., Memorial Bridge in 1975 after California state legislator George Miller Jr. A 1.7-mile (2.7 km) bridge

162-470: A Parker truss or Pratt truss than a true arch . In the Brown truss all vertical elements are under tension, with exception of the end posts. This type of truss is particularly suited for timber structures that use iron rods as tension members. See Lenticular truss below. This combines an arch with a truss to form a structure both strong and rigid. Most trusses have the lower chord under tension and

243-403: A bridge whose load-bearing superstructure is composed of a truss , a structure of connected elements, usually forming triangular units. The connected elements, typically straight, may be stressed from tension , compression , or sometimes both in response to dynamic loads. There are several types of truss bridges, including some with simple designs that were among the first bridges designed in

324-550: A Parker truss vary from near vertical in the center of the span to diagonal near each end, similar to a Warren truss. George H. Pegram , while the chief engineer of Edge Moor Iron Company in Wilmington, Delaware , patented this truss design in 1885. The Pegram truss consists of a Parker type design with the vertical posts leaning towards the center at an angle between 60 and 75°. The variable post angle and constant chord length allowed steel in existing bridges to be recycled into

405-529: A central computer which would calculate the charge according to the intersection and the time of day and add it to the car's bill. Norway has been the world's pioneer in the widespread implementation of this technology. ETC was first introduced in Bergen , in 1986, operating together with traditional tollbooths. The first major deployment of an RFID electronic toll collection system in the United States

486-599: A common truss design during this time, with their arched top chords. Companies like the Massillon Bridge Company of Massillon, Ohio , and the King Bridge Company of Cleveland , became well-known, as they marketed their designs to cities and townships. The bowstring truss design fell out of favor due to a lack of durability, and gave way to the Pratt truss design, which was stronger. Again,

567-435: A conventional truss into place or by building it in place using a "traveling support". In another method of construction, one outboard half of each balanced truss is built upon temporary falsework. When the outboard halves are completed and anchored the inboard halves may then be constructed and the center section completed as described above. The Fink truss was designed by Albert Fink of Germany in 1854. This type of bridge

648-481: A limited number of truss bridges were built. The truss may carry its roadbed on top, in the middle, or at the bottom of the truss. Bridges with the roadbed at the top or the bottom are the most common as this allows both the top and bottom to be stiffened, forming a box truss . When the roadbed is atop the truss, it is a deck truss; an example of this was the I-35W Mississippi River bridge . When

729-477: A lower chord (functioning as a suspension cable) that curves down and then up to meet at the same end points. Where the arches extend above and below the roadbed, it is called a lenticular pony truss bridge . The Pauli truss bridge is a specific variant of the lenticular truss, but the terms are not interchangeable. One type of lenticular truss consists of arcuate upper compression chords and lower eyebar chain tension links. Brunel 's Royal Albert Bridge over

810-726: A new span using the Pegram truss design. This design also facilitated reassembly and permitted a bridge to be adjusted to fit different span lengths. There are twelve known remaining Pegram span bridges in the United States with seven in Idaho , two in Kansas , and one each in California , Washington , and Utah . The Pennsylvania (Petit) truss is a variation on the Pratt truss . The Pratt truss includes braced diagonal members in all panels;

891-401: A new toll plaza with nine toll booths, two open road tolling lanes and one carpool lane at the south end of the bridge, although tolls continue to be charged only for northbound traffic. The old toll plaza at the north end of the bridge was removed. The new toll plaza was retrofitted for open road tolling to encourage FasTrak use. This required the removal of eight toll booths. The bridge is

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972-505: A newer bridge east of and parallel to the railroad bridge. It measures about 1.7 miles (2.7 km) . The new bridge carries five lanes of northbound traffic. The older bridge underwent seismic retrofits and was converted from carrying three lanes in each direction to carrying four lanes of southbound traffic and a bicycle /pedestrian lane, part of the San Francisco Bay Trail . The bridge construction included

1053-433: A one time payment online. Effective January 1, 2022 – December 31, 2024  ( 2022-01-01  – 2024-12-31 ) , the toll rate for passenger cars is $ 7. During peak traffic hours, carpool vehicles carrying three or more people, clean air vehicles, or motorcycles may pay a discounted toll of $ 3.50 if they have FasTrak and use the designated carpool lane. Drivers must pay within 48 hours after crossing

1134-459: A pin-jointed structure, one where the only forces on the truss members are tension or compression, not bending. This is used in the teaching of statics, by the building of model bridges from spaghetti . Spaghetti is brittle and although it can carry a modest tension force, it breaks easily if bent. A model spaghetti bridge thus demonstrates the use of a truss structure to produce a usefully strong complete structure from individually weak elements. In

1215-564: A regional transportation agency, in its capacity as the Bay Area Toll Authority , administers RM1 and RM2 funds, a significant portion of which are allocated to public transit capital improvements and operating subsidies in the transportation corridors served by the bridges. Caltrans administers the "second dollar" seismic surcharge, and receives some of the MTC-administered funds to perform other maintenance work on

1296-467: A specified size and/or weight to access the toll road free of charge. In 1959, Nobel Economics Prize winner William Vickrey was the first to propose a system of electronic tolling for the Washington metropolitan area. He proposed that each car would be equipped with a transponder. The transponder's personalized signal would be picked up when the car passed through an intersection and then relayed to

1377-545: A variant of the lenticular truss, "with the top chord carefully shaped so that it has a constant force along the entire length of the truss." It is named after Friedrich Augustus von Pauli  [ de ] , whose 1857 railway bridge (the Großhesseloher Brücke  [ de ] ) spanned the Isar near Munich . ( See also Grosshesselohe Isartal station .) The term Pauli truss is not interchangeable with

1458-700: Is a Pratt truss design with a polygonal upper chord. A "camelback" is a subset of the Parker type, where the upper chord consists of exactly five segments. An example of a Parker truss is the Traffic Bridge in Saskatoon , Canada. An example of a camelback truss is the Woolsey Bridge near Woolsey, Arkansas . Designed and patented in 1872 by Reuben Partridge , after local bridge designs proved ineffective against road traffic and heavy rains. It became

1539-519: Is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post, it is occasionally referred to as a Post patent truss although he never received a patent for it. The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss. A Pratt truss includes vertical members and diagonals that slope down towards the center, the opposite of

1620-446: Is a system that uses optical character recognition on images to read the license plates on vehicles. While the technology is most commonly used by law enforcement for cataloging vehicle movements and traffic enforcement, ANPR has also been used as a method of electronic toll collection. ANPR can be used in conjunction with transponder systems. If a transponder is not detected on a vehicle, a system of cameras located at each junction logs

1701-465: Is located on the north side of the span, providing an excellent view of the 3 parallel bridges passing over the Carquinez Strait with Mount Diablo in the background. It has ample parking, picnic tables and a large compass to provide orientation. This is typically the point where cyclists and pedestrians wishing to cross the bridge park their cars. Truss bridge A truss bridge is

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1782-832: Is named after the K formed in each panel by the vertical member and two oblique members. Examples include the Südbrücke rail bridge over the River Rhine, Mainz, Germany, the bridge on I-895 (Baltimore Harbor Tunnel Thruway) in Baltimore, Maryland, the Long–Allen Bridge in Morgan City, Louisiana (Morgan City Bridge) with three 600-foot-long spans, and the Wax Lake Outlet bridge in Calumet, Louisiana One of

1863-432: Is part of Interstate 680 , a major transportation link connecting other heavily traveled freeways. Between the two vehicle bridges is a Union Pacific Railroad bridge, the first bridge at this location, built between April 1929 and October 1930 by Southern Pacific . It is used by Union Pacific and BNSF ( trackage rights ) freight trains and 36 scheduled Amtrak passenger trains each weekday. Passenger trains include

1944-570: Is partly based on the Howe truss . The first Allan truss was completed on 13 August 1894 over Glennies Creek at Camberwell, New South Wales and the last Allan truss bridge was built over Mill Creek near Wisemans Ferry in 1929. Completed in March 1895, the Tharwa Bridge located at Tharwa, Australian Capital Territory , was the second Allan truss bridge to be built, the oldest surviving bridge in

2025-695: Is practical for use with spans up to 250 feet (76 m) and was a common configuration for railroad bridges as truss bridges moved from wood to metal. They are statically determinate bridges, which lend themselves well to long spans. They were common in the United States between 1844 and the early 20th century. Examples of Pratt truss bridges are the Governor's Bridge in Maryland ; the Hayden RR Bridge in Springfield, Oregon , built in 1882;

2106-416: Is relatively limited (for example, targeting only commercial vehicles and other such flagrant and/or repeat offenders). Some toll operators prefer to simply write off leakage as an expense, especially if the costs associated with collection efforts are expected to exceed the additional tolls, fees and/or fines that will likely be collected, or alternatively allow vehicles that are privately operated and/or below

2187-427: Is sufficiently stiff then this vertical element may be eliminated. If the lower chord (a horizontal member of a truss) is sufficiently resistant to bending and shear, the outer vertical elements may be eliminated, but with additional strength added to other members in compensation. The ability to distribute the forces in various ways has led to a large variety of truss bridge types. Some types may be more advantageous when

2268-407: Is supported only at the ends and is fully independent of any adjacent spans. Each span must fully support the weight of any vehicles traveling over it (the live load ). In contrast, a continuous truss functions as a single rigid structure over multiple supports. This means that the live load on one span is partially supported by the other spans, and consequently it is possible to use less material in

2349-516: Is that it relies on the honor system to the extent that without the presence of toll booths there is typically no physical means of preventing drivers who have no intention of paying the toll from accessing the road. Toll operators refer to such toll evasion as "leakage." To deter such behavior, toll operators can employ tools such as high-definition cameras to identify violators, and leakage can be offset in part or whole by fees and fines collected against offenders. However, in many cases such enforcement

2430-593: Is that the collected data can be abused by employees or stolen by computer hackers. This has led the police of Scotland to delete their collection of ANPR records in 2016. As ANPR is a new technology, its use is often not tightly regulated; it is unclear whether ANPR in Scotland complied with the UK data retention laws. All three tolled sections of New Zealand highways use ANPR. Tolls can be paid at selected gas stations, online, or by setting up an account. The following

2511-525: Is the Victoria Bridge on Prince Street, Picton, New South Wales . Also constructed of ironbark, the bridge is still in use today for pedestrian and light traffic. The Bailey truss was designed by the British in 1940–1941 for military uses during World War II. A short selection of prefabricated modular components could be easily and speedily combined on land in various configurations to adapt to

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2592-426: Is the collection of tolls on toll roads without the use of toll booths . An electronic toll collection system is usually used instead. The major advantage to ORT is that users are able to drive through the toll plaza at highway speeds without having to slow down to pay the toll. In some installations, ORT may also reduce congestion at the plazas by allowing more vehicles per hour/per lane. The disadvantage to ORT

2673-673: Is the first open road tolling facility in Northern California and the first bridge with open road tolling in California. When the Benicia–Martinez Bridge opened in 1962, tolls were $ 0.25 per car. It was set to $ 0.35 in 1970, then increased to $ 0.40 in 1976. The basic toll (for automobiles) on the seven state-owned bridges, including the Benicia–Martinez Bridge, was raised to $ 1 by Regional Measure 1, approved by Bay Area voters in 1988. A $ 1 seismic retrofit surcharge

2754-640: Is the second-longest railway bridge in North America, and the longest railway bridge west of the Mississippi River. Before the bridge was completed, ferries were used to allow the railway to cross Suisun Bay. The original ferry, built at Oakland, California in 1879 and named the Solano , was the world's largest train ferry. In 1914 the larger Contra Costa was built. In 1926 the ferries carried 93,000 passenger cars and 142,000 freight cars across

2835-519: Is used on a number of different highway systems. Both methods aims to eliminate the delay on toll roads by collecting tolls electronically by electronically debiting the accounts of registered car owners without requiring them to stop. Transponders are a receiver-transmitter that will generate a reply signal upon proper electronic interrogation. Transponders are an adaptation of military identification friend or foe technology. Most current systems rely on radio-frequency identification, where an antenna at

2916-770: The Australian Capital Territory and the oldest, longest continuously used Allan truss bridge. Completed in November 1895, the Hampden Bridge in Wagga Wagga, New South Wales , Australia, the first of the Allan truss bridges with overhead bracing, was originally designed as a steel bridge but was constructed with timber to reduce cost. In his design, Allan used Australian ironbark for its strength. A similar bridge also designed by Percy Allen

2997-621: The Dearborn River High Bridge near Augusta, Montana, built in 1897; and the Fair Oaks Bridge in Fair Oaks, California , built 1907–09. The Scenic Bridge near Tarkio, Montana , is an example of a Pratt deck truss bridge, where the roadway is on top of the truss. The queenpost truss , sometimes called "queen post" or queenspost, is similar to a king post truss in that the outer supports are angled towards

3078-1316: The Fort Wayne Street Bridge in Goshen, Indiana , the Schell Bridge in Northfield, Massachusetts , the Inclined Plane Bridge in Johnstown, Pennsylvania , the Easton–Phillipsburg Toll Bridge in Easton, Pennsylvania , the Connecticut River Bridge in Brattleboro, Vermont , the Metropolis Bridge in Metropolis, Illinois , and the Healdsburg Memorial Bridge in Healdsburg, California . A Post truss

3159-445: The Howe truss . The interior diagonals are under tension under balanced loading and vertical elements under compression. If pure tension elements (such as eyebars ) are used in the diagonals, then crossing elements may be needed near the center to accept concentrated live loads as they traverse the span. It can be subdivided, creating Y- and K-shaped patterns. The Pratt truss was invented in 1844 by Thomas and Caleb Pratt. This truss

3240-481: The River Tamar between Devon and Cornwall uses a single tubular upper chord. As the horizontal tension and compression forces are balanced these horizontal forces are not transferred to the supporting pylons (as is the case with most arch types). This in turn enables the truss to be fabricated on the ground and then to be raised by jacking as supporting masonry pylons are constructed. This truss has been used in

3321-499: The United States , because wood was in abundance, early truss bridges would typically use carefully fitted timbers for members taking compression and iron rods for tension members , usually constructed as a covered bridge to protect the structure. In 1820, a simple form of truss, Town's lattice truss , was patented, and had the advantage of requiring neither high labor skills nor much metal. Few iron truss bridges were built in

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3402-470: The long-distance trains California Zephyr and Coast Starlight and commuter-oriented Capitol Corridor services. Tolls are only collected from northbound traffic at the toll plaza on the south side of the bridge. All-electronic tolling has been in effect since 2020, and drivers may either pay using the FasTrak electronic toll collection device, using the license plate tolling program, or via

3483-461: The 19th and early 20th centuries. A truss bridge is economical to construct primarily because it uses materials efficiently. The nature of a truss allows the analysis of its structure using a few assumptions and the application of Newton's laws of motion according to the branch of physics known as statics . For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet, meaning that taken alone, every joint on

3564-489: The Bay Area Toll Authority announced plans to remove all remaining unused toll booths and create an open-road tolling system which functions at highway speeds. Union Pacific Railroad 's Benicia–Martinez drawbridge is between the two vehicle bridges. The railroad bridge was built between 1928 and 1930 for Southern Pacific Railroad to replace its train ferry between Benicia and Port Costa, California . It

3645-685: The Pennsylvania truss adds to this design half-length struts or ties in the top, bottom, or both parts of the panels. It is named after the Pennsylvania Railroad , which pioneered this design. It was once used for hundreds of bridges in the United States, but fell out of favor in the 1930s and very few examples of this design remain. Examples of this truss type include the Lower Trenton Bridge in Trenton, New Jersey ,

3726-462: The Strait. Train ferry service ended with the opening of the railroad bridge on October 15, 1930. Burlington Northern and Santa Fe Railway and Amtrak also run here on trackage rights . The drawbridge has the smallest clearances of the three bridges — lift span horizontal clearance is 291 feet and vertical clearances are 70 feet (closed) and 135 feet (open). In late 2001, construction began on

3807-471: The United States before 1850. Truss bridges became a common type of bridge built from the 1870s through the 1930s. Examples of these bridges still remain across the US, but their numbers are dropping rapidly as they are demolished and replaced with new structures. As metal slowly started to replace timber, wrought iron bridges in the US started being built on a large scale in the 1870s. Bowstring truss bridges were

3888-461: The availability of machinery, and the cost of labor. In other cases, the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics. Modern materials such as prestressed concrete and fabrication methods, such as automated welding , and the changing price of steel relative to that of labor have significantly influenced the design of modern bridges. A pure truss can be represented as

3969-713: The bridge companies marketed their designs, with the Wrought Iron Bridge Company in the lead. As the 1880s and 1890s progressed, steel began to replace wrought iron as the preferred material. Other truss designs were used during this time, including the camel-back. By the 1910s, many states developed standard plan truss bridges, including steel Warren pony truss bridges. In the 1920s and 1930s, Pennsylvania and several states continued to build steel truss bridges, using massive steel through-truss bridges for long spans. Other states, such as Michigan , used standard plan concrete girder and beam bridges, and only

4050-406: The bridge deck, they are susceptible to being hit by overheight loads when used on highways. The I-5 Skagit River bridge collapsed after such a strike; before the collapse, similar incidents had been common and had necessitated frequent repairs. Truss bridges consisting of more than one span may be either a continuous truss or a series of simple trusses. In the simple truss design, each span

4131-405: The bridge or they will be sent a toll violation invoice. No additional fees will be added to the toll violation if it is paid within 21 days. The toll plaza has nine lanes with toll booths and another nine lanes with open road tolling (ORT) in two zones. One ORT zone has two travel lanes and four shoulder lanes. The other ORT zone has one carpool travel lane with two shoulder lanes. This bridge

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4212-549: The bridges. The Bay Area Toll Authority is made up of appointed officials put in place by various city and county governments, and is not subject to direct voter oversight. Due to further funding shortages for seismic retrofit projects, the Bay Area Toll Authority again raised tolls on all seven of the state-owned bridges in July 2010. The toll rate for autos on the Benicia–Martinez Bridge was thus increased to $ 5. In June 2018, Bay Area voters approved Regional Measure 3 to further raise

4293-566: The center of the structure. The primary difference is the horizontal extension at the center which relies on beam action to provide mechanical stability. This truss style is only suitable for relatively short spans. The Smith truss , patented by Robert W Smith on July 16, 1867, has mostly diagonal criss-crossed supports. Smith's company used many variations of this pattern in the wooden covered bridges it built. Open road tolling Open road tolling ( ORT ), also called all-electronic tolling , cashless tolling , or free-flow tolling ,

4374-732: The center, the opposite of the Pratt truss . In contrast to the Pratt truss, the diagonal web members are in compression and the vertical web members are in tension. Few of these bridges remain standing. Examples include Jay Bridge in Jay, New York ; McConnell's Mill Covered Bridge in Slippery Rock Township, Lawrence County, Pennsylvania ; Sandy Creek Covered Bridge in Jefferson County, Missouri ; and Westham Island Bridge in Delta, British Columbia , Canada. The K-truss

4455-497: The center. Many cantilever bridges, like the Quebec Bridge shown below, have two cantilever spans supporting a simple truss in the center. The bridge would remain standing if the simple truss section were removed. Bridges are the most widely known examples of truss use. There are many types, some of them dating back hundreds of years. Below are some of the more common designs. The Allan truss , designed by Percy Allan ,

4536-414: The compression members and to control deflection. It is mainly used for rail bridges, showing off a simple and very strong design. In the Pratt truss the intersection of the verticals and the lower horizontal tension members are used to anchor the supports for the short-span girders under the tracks (among other things). With the Baltimore truss, there are almost twice as many points for this to happen because

4617-600: The construction of a stadium, with the upper chords of parallel trusses supporting a roof that may be rolled back. The Smithfield Street Bridge in Pittsburgh, Pennsylvania , is another example of this type. An example of a lenticular pony truss bridge that uses regular spans of iron is the Turn-of-River Bridge designed and manufactured by the Berlin Iron Bridge Co. The Pauli truss is

4698-484: The earliest examples is the Old Blenheim Bridge , which with a span of 210 feet (64 m) and a total length of 232 feet (71 m) long was the second-longest covered bridge in the United States, until its destruction from flooding in 2011. The Busching bridge, often erroneously used as an example of a Long truss, is an example of a Howe truss, as the verticals are metal rods. A Parker truss bridge

4779-401: The elements, as in a Vierendeel truss . In the bridge illustrated in the infobox at the top, vertical members are in tension, lower horizontal members in tension, shear , and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension. The central vertical member stabilizes the upper compression member, preventing it from buckling . If the top member

4860-514: The largest lightweight concrete segmental bridge in California . The estimated cost was $ 1.05 billion, the final cost was $ 1.3 billion. The original estimated cost was around $ 300 million, it is noted for its large delay in construction and large over cost (over $ 1 billion). The project's cost overshadowed the replacement of the Cypress Freeway portion of Interstate 880 . The new bridge opened at 10:30pm on August 25, 2007. A vista point

4941-412: The needs at the site and allow rapid deployment of completed trusses. In the image, note the use of pairs of doubled trusses to adapt to the span and load requirements. In other applications the trusses may be stacked vertically, and doubled as necessary. The Baltimore truss is a subclass of the Pratt truss. A Baltimore truss has additional bracing in the lower section of the truss to prevent buckling in

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5022-574: The short verticals will also be used to anchor the supports. Thus the short-span girders can be made lighter because their span is shorter. A good example of the Baltimore truss is the Amtrak Old Saybrook – Old Lyme Bridge in Connecticut , United States. The Bollman Truss Railroad Bridge at Savage, Maryland , United States is the only surviving example of a revolutionary design in the history of American bridge engineering. The type

5103-451: The simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support. This type of bridge uses a substantial number of lightweight elements, easing the task of construction. Truss elements are usually of wood, iron, or steel. A lenticular truss bridge includes a lens-shape truss, with trusses between an upper chord functioning as an arch that curves up and then down to end points, and

5184-454: The standard for covered bridges built in central Ohio in the late 1800s and early 1900s. The Pegram truss is a hybrid between the Warren and Parker trusses where the upper chords are all of equal length and the lower chords are longer than the corresponding upper chord. Because of the difference in upper and lower chord length, each panel is not square. The members which would be vertical in

5265-476: The state-owned bridges to all-electronic tolling , citing that 80 percent of drivers are now using FasTrak and the change would improve traffic flow. On March 20, 2020, accelerated by the COVID-19 pandemic , all-electronic tolling was placed in effect for all seven state-owned toll bridges. The MTC then installed new systems at all seven bridges to make them permanently cashless by the start of 2021. In April 2022,

5346-464: The structure is functionally considered to be a flexible joint as opposed to a rigid joint with the strength to maintain its shape, and the resulting shape and strength of the structure are only maintained by the interlocking of the components. This assumption means that members of the truss (chords, verticals, and diagonals) will act only in tension or compression. A more complex analysis is required where rigid joints impose significant bending loads upon

5427-409: The term lenticular truss and, according to Thomas Boothby, the casual use of the term has clouded the literature. The Long truss was designed by Stephen H. Long in 1830. The design resembles a Howe truss , but is entirely made of wood instead of a combination of wood and metal. The longest surviving example is the Eldean Covered Bridge north of Troy, Ohio , spanning 224 feet (68 m). One of

5508-421: The toll gate communicates with a transponder on the vehicle via dedicated short-range communications (DSRC). Some early systems used barcodes affixed to each vehicle, to be read optically at the toll booth. Optical systems proved to have poor reading reliability, especially when faced with inclement weather and dirty vehicles. Automatic number plate recognition (ANPR) or an automatic license plate reader (ALPR)

5589-412: The tolls on all seven of the state-owned bridges to fund $ 4.5 billion worth of transportation improvements in the area. Under the passed measure, the toll rate for autos on the Benicia–Martinez Bridge will be increased to $ 6 on January 1, 2019; to $ 7 on January 1, 2022; and then to $ 8 on January 1, 2025. In September 2019, the MTC approved a $ 4 million plan to eliminate toll takers and convert all seven of

5670-489: The truss members are both above and below the roadbed it is called a through truss; an example of this is the Pulaski Skyway , and where the sides extend above the roadbed but are not connected, a pony truss or half-through truss. Sometimes both the upper and lower chords support roadbeds, forming a double-decked truss . This can be used to separate rail from road traffic or to separate the two directions of road traffic. Since through truss bridges have supports located over

5751-471: The truss. Continuous truss bridges were not very common before the mid-20th century because they are statically indeterminate , which makes them difficult to design without the use of computers . A multi-span truss bridge may also be constructed using cantilever spans, which are supported at only one end rather than both ends like other types of trusses. Unlike a continuous truss, a cantilever truss does not need to be connected rigidly, or indeed at all, at

5832-428: The upper chord under compression. In a cantilever truss the situation is reversed, at least over a portion of the span. The typical cantilever truss bridge is a "balanced cantilever", which enables the construction to proceed outward from a central vertical spar in each direction. Usually these are built in pairs until the outer sections may be anchored to footings. A central gap, if present, can then be filled by lifting

5913-495: The vehicle's unique identity and an invoice is mailed. The use of ANPR reduces fraud related to cash transactions or non-payment, makes charging effective, and reduces the amount of required manpower to enforce the toll road, but requires expensive computer software. However, ANPR usage raises questions over privacy and data protection . ANPR allows police to automatically compile vast databases of innocent road users' movements, thus invading their privacy. Another concern

5994-430: The wood is employed for compression elements while other types may be easier to erect in particular site conditions, or when the balance between labor, machinery, and material costs has certain favorable proportions. The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection,

6075-461: The world using electronic toll collection technologies, and ORT has opened the feasibility to implement congestion pricing policies in urban areas. Collection of tolls on open toll roads is usually conducted through either the use of transponders or automatic plate recognition, the vast majority of which utilizes an overhead gantry system above the road. While rarely used as the primary vehicle identification method, automatic number plate recognition

6156-431: Was added in 1998 by the state legislature, originally for eight years, but since then extended to December 2037 (AB1171, October 2001). On March 2, 2004, voters approved Regional Measure 2, raising the toll by another dollar to a total of $ 3. An additional dollar was added to the toll starting January 1, 2007, to cover cost overruns concerning the replacement of the eastern span. The Metropolitan Transportation Commission ,

6237-414: Was also easy to assemble. Wells Creek Bollman Bridge is the only other bridge designed by Wendel Bollman still in existence, but it is a Warren truss configuration. The bowstring truss bridge was patented in 1841 by Squire Whipple . While similar in appearance to a tied-arch bridge , a bowstring truss has diagonal load-bearing members: these diagonals result in a structure that more closely matches

6318-511: Was built alongside and opened on August 25, 2007 with five lanes of northbound traffic. In 2007, it was named the Congressman George Miller Benicia–Martinez Bridge after U.S. Congressman George Miller III , Miller Jr.'s son. The cost of the 1962 span was US$ 25 million and US$ 1.3 billion for the 2007 span. (Adjusted for inflation , equivalent to $ 252 million and $ 1.91 billion respectively.) The bridge

6399-405: Was named after its inventor, Wendel Bollman , a self-educated Baltimore engineer. It was the first successful all-metal bridge design (patented in 1852) to be adopted and consistently used on a railroad. The design employs wrought iron tension members and cast iron compression members. The use of multiple independent tension elements reduces the likelihood of catastrophic failure. The structure

6480-683: Was popular with the Baltimore and Ohio Railroad . The Appomattox High Bridge on the Norfolk and Western Railway included 21 Fink deck truss spans from 1869 until their replacement in 1886. There are also inverted Fink truss bridges such as the Moody Pedestrian Bridge in Austin, Texas. The Howe truss , patented in 1840 by Massachusetts millwright William Howe , includes vertical members and diagonals that slope up towards

6561-709: Was the TollTag system used on the Dallas North Tollway , implemented in 1989 by Amtech . The first fully automated toll highway in the world, Ontario Highway 407 , opened in Canada on June 7, 1997. The highway managed to achieve this automation through the use of both RFID technology and automatic number-plate recognition . In September 1998, Singapore became the first city in the world to implement an electronic road toll collection system for purposes of congestion pricing . Today there are many roads around

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