70-664: The Antelope Valley Press , colloquially referred to as the Valley Press or AV Press by its staff and Antelope Valley residents, is the largest-circulation daily newspaper in Palmdale , California , United States. The Valley Press covers the fast-growing Antelope Valley, especially the Palmdale/ Lancaster Urbanized Area (a US Census Bureau defined term) and adjacent areas of north Los Angeles and southeastern Kern counties, including
140-508: A slipformed (or pre-cast) concrete base (development 2000s). The 'embedded rail structure', used in the Netherlands since 1976, initially used a conventional UIC 54 rail embedded in concrete, and later developed (late 1990s) to use a 'mushroom' shaped SA42 rail profile; a version for light rail using a rail supported in an asphalt concrete –filled steel trough has also been developed (2002). Modern ladder track can be considered
210-599: A train track or permanent way (often " perway " in Australia or " P Way " in Britain and India), is the structure on a railway or railroad consisting of the rails , fasteners , railroad ties (sleepers, British English) and ballast (or slab track ), plus the underlying subgrade . It enables trains to move by providing a dependable surface for their wheels to roll upon. Early tracks were constructed with wooden or cast iron rails, and wooden or stone sleepers; since
280-440: A "clickety-clack" sound. Unless it is well-maintained, jointed track does not have the ride quality of welded rail and is less desirable for high speed trains . However, jointed track is still used in many countries on lower speed lines and sidings , and is used extensively in poorer countries due to the lower construction cost and the simpler equipment required for its installation and maintenance. A major problem of jointed track
350-415: A continuous reinforced concrete slab and the use of pre-cast pre-stressed concrete units laid on a base layer. Many permutations of design have been put forward. However, ballastless track has a high initial cost, and in the case of existing railroads the upgrade to such requires closure of the route for a long period. Its whole-life cost can be lower because of the reduction in maintenance. Ballastless track
420-481: A development of baulk road. Ladder track utilizes sleepers aligned along the same direction as the rails with rung-like gauge restraining cross members. Both ballasted and ballastless types exist. Modern track typically uses hot-rolled steel with a profile of an asymmetrical rounded I-beam . Unlike some other uses of iron and steel , railway rails are subject to very high stresses and have to be made of very high-quality steel alloy. It took many decades to improve
490-622: A scientific observation of the valley in 1844. After Fremont's visit the 49ers crossed the valley via the Old Tejon Pass into the San Joaquin Valley on their way to the gold fields. Later, a better wagon road, the Stockton – Los Angeles Road route to Tejon Pass , followed in 1854. Stagecoach lines across the southern foothills came through the valley along this wagon road, and were the preferred method for travelers before
560-465: A temperature roughly midway between the extremes experienced at that location. (This is known as the "rail neutral temperature".) This installation procedure is intended to prevent tracks from buckling in summer heat or pulling apart in the winter cold. In North America, because broken rails are typically detected by interruption of the current in the signaling system, they are seen as less of a potential hazard than undetected heat kinks. Joints are used in
630-471: Is 115 to 141 lb/yd (57 to 70 kg/m). In Europe, rail is graded in kilograms per metre and the usual range is 40 to 60 kg/m (81 to 121 lb/yd). The heaviest mass-produced rail was 155 pounds per yard (77 kg/m), rolled for the Pennsylvania Railroad . The rails used in rail transport are produced in sections of fixed length. Rail lengths are made as long as possible, as
700-408: Is a manual process requiring a reaction crucible and form to contain the molten iron. North American practice is to weld 1 ⁄ 4 -mile-long (400 m) segments of rail at a rail facility and load it on a special train to carry it to the job site. This train is designed to carry many segments of rail which are placed so they can slide off their racks to the rear of the train and be attached to
770-554: Is bounded by the Garlock and San Andreas fault systems. Precipitation in the surrounding mountain ranges contributes to groundwater recharge . The Antelope Valley is home to a wide range of plants and animals. This includes hundreds of plants such as the California juniper , Joshua tree , California scrub oak , creosote , and wildflowers, notably the California poppy . Winter brings much-needed rain, which slowly penetrates
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#1732791412424840-494: Is cracking around the bolt holes, which can lead to breaking of the rail head (the running surface). This was the cause of the Hither Green rail crash which caused British Railways to begin converting much of its track to continuous welded rail. Where track circuits exist for signalling purposes, insulated block joints are required. These compound the weaknesses of ordinary joints. Specially-made glued joints, where all
910-466: Is graded by its linear density , that is, its mass over a standard length. Heavier rail can support greater axle loads and higher train speeds without sustaining damage than lighter rail, but at a greater cost. In North America and the United Kingdom, rail is graded in pounds per yard (usually shown as pound or lb ), so 130-pound rail would weigh 130 lb/yd (64 kg/m). The usual range
980-646: Is located in northern Los Angeles County, California , United States, and the southeast portion of California's Kern County , and constitutes the western tip of the Mojave Desert . It is situated between the Tehachapi , Sierra Pelona , and the San Gabriel Mountains . The valley was named for the pronghorns that roamed there until they were all eliminated in the 1880s, mostly by hunting, or resettled in other areas. The principal cities in
1050-747: Is located near Boron . Also, several private and home-school high schools arein the area, most notably: The Antelope Valley Symphony Orchestra is a professional ensemble that performs four concerts each year at the Lancaster Performing Arts Center. It is an auxiliary of Antelope Valley College, and performs regularly with the Antelope Valley College Civic Orchestra. Antelope Valley Indian Museum State Historic Park has been featured in films such as The Magnificent Seven Ride! (1972) and The Stone Killer (1973). Mackenna's Gold (1964)
1120-838: Is over 50 miles (80 km) away. Include: On the ridgeline of the San Gabriel Mountains, the Angeles Crest Highway ( State Route 2 ) snakes 60 miles (100 km) through the Angeles National Forest to La Cañada Flintridge and the Greater Los Angeles metropolitan region. Some people of note have spent time in the valley, including: Over 10,000 population Under 10,000 population Railroad track A railway track ( British English and UIC terminology ) or railroad track ( American English ), also known as
1190-402: Is scarce and where tonnage or speeds are high. Steel is used in some applications. The track ballast is customarily crushed stone, and the purpose of this is to support the sleepers and allow some adjustment of their position, while allowing free drainage. A disadvantage of traditional track structures is the heavy demand for maintenance, particularly surfacing (tamping) and lining to restore
1260-456: Is starting to paint rails white to lower the peak temperatures reached in summer days. After new segments of rail are laid, or defective rails replaced (welded-in), the rails can be artificially stressed if the temperature of the rail during laying is cooler than what is desired. The stressing process involves either heating the rails, causing them to expand, or stretching the rails with hydraulic equipment. They are then fastened (clipped) to
1330-767: Is to bolt them together using metal fishplates (jointbars in the US), producing jointed track . For more modern usage, particularly where higher speeds are required, the lengths of rail may be welded together to form continuous welded rail (CWR). Jointed track is made using lengths of rail, usually around 20 m (66 ft) long (in the UK) and 39 or 78 ft (12 or 24 m) long (in North America), bolted together using perforated steel plates known as fishplates (UK) or joint bars (North America). Fishplates are usually 600 mm (2 ft) long, used in pairs either side of
1400-435: Is usually considered for new very high speed or very high loading routes, in short extensions that require additional strength (e.g. railway stations), or for localised replacement where there are exceptional maintenance difficulties, for example in tunnels. Most rapid transit lines and rubber-tyred metro systems use ballastless track. Early railways (c. 1840s) experimented with continuous bearing railtrack, in which
1470-620: The Philippines were the most common foreign places of birth in 2000 in Northwest Antelope Valley. Mexico and El Salvador were the most common foreign places of birth in the northwest. German and English were the most common ancestries in the northeast. German and Irish were the most common ancestries in Southeast Antelope Valley. Mexico and Colombia were the common foreign places of birth in
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#17327914124241540-648: The Sacramento-San Joaquin River Delta in northern California has caused and causes adverse environmental and social effects in the delta: "Over decades, [the] competing uses for water supply and habitat have jeopardized the Delta's ability to meet either need. All stakeholders agree the estuary is in trouble and requires long-term solutions to ensure reliable, quality water supplies and a healthy ecosystem." The Antelope Valley's population growth and development place considerable stress on
1610-615: The 1770s, during the colonization of North America . Father Francisco Garcés , a Spanish Franciscan friar, is believed to have traveled the west end of the valley in 1776. The Spanish established El Camino Viejo through the western part of the valley between Los Angeles and the missions of the San Francisco Bay in the 1780s. By 1808, the Spanish had moved the native people out of the valley and into missions. Jedediah Smith came through in 1827, and John C. Fremont made
1680-588: The 1870s, rails have almost universally been made from steel. The first railway in Britain was the Wollaton Wagonway , built in 1603 between Wollaton and Strelley in Nottinghamshire. It used wooden rails and was the first of around 50 wooden-railed tramways built over the next 164 years. These early wooden tramways typically used rails of oak or beech, attached to wooden sleepers with iron or wooden nails. Gravel or small stones were packed around
1750-719: The Antelope Valley are Palmdale and Lancaster . The Antelope Valley comprises the western tip of the Mojave Desert , opening up to the Victor Valley and the Great Basin to the east. Lying north of the San Gabriel Mountains , southeast of the Tehachapis , and east of the Sierra Pelona Mountains , this desert ecosystem spans around 2,200 sq mi (5,698 km ). The valley
1820-529: The Antelope Valley depends mainly on pumping of groundwater from the valley's aquifers and on importing additional water from the California Aqueduct . Long-term groundwater pumping has lowered the water table , thereby increasing pumping lifts, reducing well efficiency, and causing land subsidence . While aqueducts supply additional water that meets increasing human demand for agricultural, industrial, and domestic uses, diversion of water from
1890-402: The area's dry ground, bringing up native grasses and wildflowers. Poppy season depends completely on the precipitation, but a good bloom can be killed off by the unusual weather in the late winter and early spring. The Antelope Valley gets its name from its history of pronghorn grazing in large numbers. In 1882-85, the valley lost 30,000 head of antelope, almost half of the species for which it
1960-400: The bolt heads on the same side of the rail. Small gaps which function as expansion joints are deliberately left between the rail ends to allow for expansion of the rails in hot weather. European practice was to have the rail joints on both rails adjacent to each other, while North American practice is to stagger them. Because of these small gaps, when trains pass over jointed tracks they make
2030-549: The coming of the Southern Pacific Railroad in 1876. The rail service linking the valley to the Central Valley and Los Angeles started its first large influx of white settlers, and farms and towns soon sprouted on the valley floor. The aircraft (now called aerospace) industry took hold in the valley at Plant 42 in 1952. Edwards AFB, then called Muroc Army Air Field, was established in 1933. The area
2100-465: The continuous welded rail when necessary, usually for signal circuit gaps. Instead of a joint that passes straight across the rail, the two rail ends are sometimes cut at an angle to give a smoother transition. In extreme cases, such as at the end of long bridges, a breather switch (referred to in North America and Britain as an expansion joint ) gives a smooth path for the wheels while allowing
2170-440: The desired track geometry and smoothness of vehicle running. Weakness of the subgrade and drainage deficiencies also lead to heavy maintenance costs. This can be overcome by using ballastless track. In its simplest form this consists of a continuous slab of concrete (like a highway structure) with the rails supported directly on its upper surface (using a resilient pad). There are a number of proprietary systems; variations include
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2240-500: The early 1900s caused a scarcity in bunch grass , their main food source. Now, the sighting of a pronghorn is rare, although a small number remain in the western portion of the valley. Common game species in the Antelope Valley include mule deer and mountain quail . Other common species in the Antelope Valley include the golden-mantled ground squirrel , Beechey ground squirrel , red-tailed hawk , Cooper's hawk , Stellar's jay , leopard frog , and rattlesnake . Human water use in
2310-421: The early 1980s to around three times its former level. Major retail has followed the population influx, centered on Palmdale's Antelope Valley Mall . The Lancaster—Palmdale urbanized area is home to 372,287 people. Some long-term residents living far out in the desert have been cited by Los Angeles County's nuisance abatement teams for code violations, forcing residents to either make improvements or move. One of
2380-440: The end of one rail to expand relative to the next rail. A sleeper (tie or crosstie) is a rectangular object on which the rails are supported and fixed. The sleeper has two main roles: to transfer the loads from the rails to the track ballast and the ground underneath, and to hold the rails to the correct width apart (to maintain the rail gauge ). They are generally laid transversely to the rails. Various methods exist for fixing
2450-428: The gaps are filled with epoxy resin , increase the strength again. As an alternative to the insulated joint, audio frequency track circuits can be employed using a tuned loop formed in approximately 20 m (66 ft) of the rail as part of the blocking circuit. Some insulated joints are unavoidable within turnouts. Another alternative is an axle counter , which can reduce the number of track circuits and thus
2520-626: The intrinsic weakness in resisting vertical loading results in the ballast becoming depressed and a heavy maintenance workload is imposed to prevent unacceptable geometrical defects at the joints. The joints also needed to be lubricated, and wear at the fishplate (joint bar) mating surfaces needed to be rectified by shimming. For this reason jointed track is not financially appropriate for heavily operated railroads. Timber sleepers are of many available timbers, and are often treated with creosote , chromated copper arsenate , or other wood preservatives. Pre-stressed concrete sleepers are often used where timber
2590-480: The iron came loose, began to curl, and intruded into the floors of the coaches. The iron strap rail coming through the floors of the coaches came to be referred to as "snake heads" by early railroaders. The Deeside Tramway in North Wales used this form of rail. It opened around 1870 and closed in 1947, with long sections still using these rails. It was one of the last uses of iron-topped wooden rails. Rail
2660-402: The joints between rails are a source of weakness. Throughout the history of rail production, lengths have increased as manufacturing processes have improved. The following are lengths of single sections produced by steel mills , without any thermite welding . Shorter rails may be welded with flashbutt welding , but the following rail lengths are unwelded. Welding of rails into longer lengths
2730-476: The lake beds offer a vast landing area. Although NASA later built a landing strip at Kennedy Space Center , Edwards was retained as the backup in case of bad weather at Cape Canaveral . NASA Neil A. Armstrong Flight Research Center is a tenant organization at Edwards AFB. The center is best known for the X-15 experimental rocket ship program. It has been the home of NASA's high-performance aircraft research since it
2800-605: The local and regional water systems. According to David Leighton of the United States Geological Survey : "A deliberate management effort will be required to meet future water demand in the Antelope Valley without incurring significant economic and environmental costs associated with overuse of the ground-water resource." The first peoples of the Antelope Valley include the Kawaiisu , Kitanemuk , Serrano , and Tataviam . Europeans first entered in
2870-615: The manufacturing and integration and testing of new military aviation equipment. With the size of the industry there, Antelope Valley has been nicknamed the Aerospace Valley. The valley's first main industry as a part of the United States was agriculture . Historically known in the region for its extensive alfalfa fields and fruit crops, farmers now are growing a wider variety of crops, such as carrots, onions, lettuce, and potatoes. As housing tracts continue to build in
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2940-888: The mid- to late-20th century used rails 39 feet (11.9 m) long so they could be carried in gondola cars ( open wagons ), often 40 feet (12.2 m) long; as gondola sizes increased, so did rail lengths. According to the Railway Gazette International the planned-but-cancelled 150-kilometre rail line for the Baffinland Iron Mine , on Baffin Island , would have used older carbon steel alloys for its rails, instead of more modern, higher performance alloys, because modern alloy rails can become brittle at very low temperatures. Early North American railroads used iron on top of wooden rails as an economy measure but gave up this method of construction after
3010-543: The middle of the valley, the farm operations are found farther to the west and east sides than in earlier decades. The northern reaches of Antelope Valley are part of the Tehachapi Wind Resource Area , the largest wind resource area in California. The valley also has numerous solar farms , some of which are among the largest in the United States . The world's largest open-pit borax mine
3080-581: The newly dedicated Mojave Air and Space Port . The spaceport is famous as the base of operations for Scaled Composites , the company that designed SpaceShipOne and won the X-Prize . Much of the work done at these facilities is performed in coordination with Edwards Air Force Base and the NASA Dryden Flight Research Center (see above), from the creation and testing of proof-of-concept X-planes, to Space Shuttle operations, to
3150-620: The number of insulated rail joints required. Most modern railways use continuous welded rail (CWR), sometimes referred to as ribbon rails or seamless rails . In this form of track, the rails are welded together by utilising flash butt welding to form one continuous rail that may be several kilometres long. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less maintenance; trains can travel on it at higher speeds and with less friction. Welded rails are more expensive to lay than jointed tracks, but have much lower maintenance costs. The first welded track
3220-404: The outside of sharp curves compared to the rails on the inside. Rails can be supplied pre-drilled with boltholes for fishplates or without where they will be welded into place. There are usually two or three boltholes at each end. Rails are produced in fixed lengths and need to be joined end-to-end to make a continuous surface on which trains may run. The traditional method of joining the rails
3290-484: The properties is a church building that was used as a filming location for Kill Bill . The code enforcers have arrived on some of their visits in SWAT -team formats. Hispanics and Whites make up the majority of the population. Spanish and Tagalog are the most common foreign languages spoken in the Antelope Valley. According to Mapping L.A. , German and English were the most common ancestries and Mexico and
3360-423: The quality of the materials, including the change from iron to steel. The stronger the rails and the rest of the trackwork, the heavier and faster the trains the track can carry. Other profiles of rail include: bullhead rail ; grooved rail ; flat-bottomed rail (Vignoles rail or flanged T-rail); bridge rail (inverted U–shaped used in baulk road ); and Barlow rail (inverted V). North American railroads until
3430-682: The rail by special clips that resist longitudinal movement of the rail. There is no theoretical limit to how long a welded rail can be. However, if longitudinal and lateral restraint are insufficient, the track could become distorted in hot weather and cause a derailment. Distortion due to heat expansion is known in North America as sun kink , and elsewhere as buckling. In extreme hot weather special inspections are required to monitor sections of track known to be problematic. In North American practice, extreme temperature conditions will trigger slow orders to allow for crews to react to buckling or "sun kinks" if encountered. The German railway company Deutsche Bahn
3500-425: The rail ends and bolted together (usually four, but sometimes six bolts per joint). The bolts have alternating orientations so that in the event of a derailment and a wheel flange striking the joint, only some of the bolts will be sheared, reducing the likelihood of the rails misaligning with each other and exacerbating the derailment. This technique is not applied universally; European practice being to have all
3570-500: The rail to the sleeper. Historically, spikes gave way to cast iron chairs fixed to the sleeper. More recently, springs (such as Pandrol clips ) are used to fix the rail to the sleeper chair. Sometimes rail tracks are designed to be portable and moved from one place to another as required. During construction of the Panama Canal , tracks were moved around excavation works. These track gauge were 5 ft ( 1,524 mm ) and
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#17327914124243640-655: The rail was supported along its length, with examples including Brunel's baulk road on the Great Western Railway , as well as use on the Newcastle and North Shields Railway , on the Lancashire and Yorkshire Railway to a design by John Hawkshaw , and elsewhere. Continuous-bearing designs were also promoted by other engineers. The system was tested on the Baltimore and Ohio railway in the 1840s, but
3710-562: The rolling stock full size. Portable tracks have often been used in open pit mines. In 1880 in New York City , sections of heavy portable track (along with much other improvised technology) helped in the move of the ancient obelisk in Central Park to its final location from the dock where it was unloaded from the cargo ship SS Dessoug . Cane railways often had permanent tracks for the main lines, with portable tracks serving
3780-426: The sleepers in their expanded form. This process ensures that the rail will not expand much further in subsequent hot weather. In cold weather the rails try to contract, but because they are firmly fastened, cannot do so. In effect, stressed rails are a bit like a piece of stretched elastic firmly fastened down. In extremely cold weather, rails are heated to prevent "pull aparts". CWR is laid (including fastening) at
3850-617: The sleepers to hold them in place and provide a walkway for the people or horses that moved wagons along the track. The rails were usually about 3 feet (0.91 m) long and were not joined - instead, adjacent rails were laid on a common sleeper. The straight rails could be angled at these joints to form primitive curved track. The first iron rails laid in Britain were at the Darby Ironworks in Coalbrookdale in 1767. When steam locomotives were introduced, starting in 1804,
3920-540: The sleepers with base plates that spread the load. When concrete sleepers are used, a plastic or rubber pad is usually placed between the rail and the tie plate. Rail is usually attached to the sleeper with resilient fastenings, although cut spikes are widely used in North America. For much of the 20th century, rail track used softwood timber sleepers and jointed rails, and a considerable amount of this track remains on secondary and tertiary routes. In North America and Australia, flat-bottomed rails were typically fastened to
3990-480: The sleepers with dog spikes through a flat tie plate. In Britain and Ireland, bullhead rails were carried in cast-iron chairs which were spiked to the sleepers. In 1936, the London, Midland and Scottish Railway pioneered the conversion to flat-bottomed rail in Britain, though earlier lines had made some use of it. Jointed rails were used at first because contemporary technology did not offer any alternative. However,
4060-487: The southeast. Edwards Air Force Base lies east of Rosamond , 37 miles (60 km) northeast of Palmdale . Edwards AFB's dry lakebeds are the lowest geographic elevation in the valley. Significant numbers of U.S. military test flights are performed there, and it has been the site of many important aeronautical accomplishments, including the first flight to break the sound barrier , accomplished by Chuck Yeager. NASA Space Shuttles originally landed at Edwards because
4130-511: The ties (sleepers) in a continuous operation. If not restrained, rails would lengthen in hot weather and shrink in cold weather. To provide this restraint, the rail is prevented from moving in relation to the sleeper by use of clips or anchors. Attention needs to be paid to compacting the ballast effectively, including under, between, and at the ends of the sleepers, to prevent the sleepers from moving. Anchors are more common for wooden sleepers, whereas most concrete or steel sleepers are fastened to
4200-620: The time, the Valley was home to about 3,500 people. Over the decades of the 20th century, the newspaper changed hands, and there were a few name changes as well. On May 4, 1950, the paper became known as the South Antelope Valley Press . It had been a family-owned business since beginning as a weekly newspaper in 1915, until June 30, 2017, when it was assimilated into Canadian publisher Steven Malkowich's consortium of holdings. Antelope Valley The Antelope Valley
4270-406: The track then in use proved too weak to carry the additional weight. Richard Trevithick 's pioneering locomotive at Pen-y-darren broke the plateway track and had to be withdrawn. As locomotives became more widespread in the 1810s and 1820s, engineers built rigid track formations, with iron rails mounted on stone sleepers, and cast-iron chairs holding them in place. This proved to be a mistake, and
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#17327914124244340-466: The upscale Los Angeles urban escapes of Acton and Agua Dulce . Other areas the Valley Press occasionally covers, particularly for aerospace related stories and local high school and college level sports, include the Victor Valley , Bakersfield , and southern San Joaquin Valley areas. The Valley Press was founded by A.J. Hicks on Saturday, April 3, 1915, as the Palmdale Post . At
4410-668: Was also partly filmed in Antelope Valley. The video to the R.E.M. song " Man on the Moon " was shot in Antelope Valley in October 1992. Major hospitals include: The Antelope Valley was formerly served by a county hospital, High Desert Hospital, which was converted into an urgent care clinic in 2003 due to the county's budget problems. As a result, indigent patients with serious but non-life-threatening medical conditions must seek treatment at Olive View – UCLA Medical Center in Sylmar, which
4480-467: Was first introduced around 1893, making train rides quieter and safer. With the introduction of thermite welding after 1899, the process became less labour-intensive, and ubiquitous. Modern production techniques allowed the production of longer unwelded segments. Newer longer rails tend to be made as simple multiples of older shorter rails, so that old rails can be replaced without cutting. Some cutting would be needed as slightly longer rails are needed on
4550-432: Was found to be more expensive to maintain than rail with cross sleepers . This type of track still exists on some bridges on Network Rail where the timber baulks are called waybeams or longitudinal timbers. Generally the speed over such structures is low. Later applications of continuously supported track include Balfour Beatty 's 'embedded slab track', which uses a rounded rectangular rail profile (BB14072) embedded in
4620-648: Was founded for the X-1 program. The Space Shuttle orbiter was serviced there when it landed at Edwards. U. S. Air Force Plant 42 in northeast Palmdale is home to Lockheed Martin , Boeing , Northrop Grumman , and BAE Systems , among other aerospace-related companies. Notable projects assembled and/or designed there include the Space Shuttle orbiters , B-1 Lancer bombers, B-2 Spirit bombers, F-117 Nighthawk fighters, F-35 Joint Strike Fighters , and Lockheed L-1011 Tristar passenger jets. This region also houses
4690-410: Was named. Unusually heavy snows in both the mountains and the valley floor drove the antelope toward their normal feeding grounds in the eastern part of the valley. Since they would not cross the railroad tracks , many of them starved to death. The remainder of these pronghorns were hunted for their hides by settlers. Once abundant, they either died off or migrated into the Central Valley . A drought in
4760-480: Was once under Mexican rule and was named after the large herds of antelope. In recent decades, the valley has become a bedroom community to the Greater Los Angeles area . Major housing-tract development and population growth took off beginning in 1983, which has increased the population of Palmdale around 12 times its former size as of 2006. Neighboring Lancaster has increased its population since
4830-466: Was soon replaced with flexible track structures that allowed a degree of elastic movement as trains passed over them. Traditionally, tracks are constructed using flat-bottomed steel rails laid on and spiked or screwed into timber or pre-stressed concrete sleepers (known as ties in North America), with crushed stone ballast placed beneath and around the sleepers. Most modern railroads with heavy traffic use continuously welded rails that are attached to
4900-505: Was used in Germany in 1924. and has become common on main lines since the 1950s. The preferred process of flash butt welding involves an automated track-laying machine running a strong electric current through the touching ends of two unjoined rails. The ends become white hot due to electrical resistance and are then pressed together forming a strong weld. Thermite welding is used to repair or splice together existing CWR segments. This
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