Social and Environmental Effects
By reducing travel times relative to arterial streets, highways have a positive effect upon balance of leisure or productive time through reduced commute and other travel time. However, highways have criticisms, partially due to being an extended linear source of pollution:
· Community cohesion: Where highways are created through existing communities, there can be reduced community cohesion and more difficult local access.
· Roadway noise: Highways generate more roadway noise than arterial streets due to the higher operating speeds. Therefore, considerable noise health effects are expected from highway systems. Noise mitigation strategies exist to reduce sound levels at nearby sensitive receptors. The idea that highway design could be influenced by acoustical engineering considerations first arose about 1973.
· Air quality issues: Highways may contribute fewer emissions than arterials carrying the same vehicle volumes. This is because high, constant-speed operation creates an emission reduction compared to vehicular flows with stops and starts. However, concentrations of air pollutants near highways may be higher due to increased traffic volumes. Therefore, the risk of exposure to elevated levels of air pollutants from a highway may be considerable, and further magnified when highways have traffic congestion.
· New highways can cause habitat fragmentation and allow human intrusion into previously untouched areas.
Unit 10 Motorway
Motorway symbol in the UK, France and Ireland.
A motorway (in the United Kingdom, New Zealand, Pakistan, some other Commonwealth nations and Ireland) is both a type of road and a classification or designation. Motorways are highways designed to carry a large volume of traffic where a normal road would not suffice or would be unsafe, usually between cities. In the UK they are predominantly dual-carriageway roads, usually with three lanes in each direction, although four-lane and two-lane carriageways are also common, and all have grade-separated access.
Equivalent terms in other countries include autoroute, autobahn, freeway, autostrada, autopista, motorvej, autópálya, motorväg and autoput. In North America, the English terms freeway and expressway (including autoroutes) are used as a type of road, not necessarily as a classification type. Many highways are maintained throughout the United States as part of the Interstate Highway System. These highways are generally similar to motorways in purpose and quality.
Regulations and Features
A Sunday in April 2004 at 5 p.m. on Britain's busy M25
In Ireland and the UK, motorways are denoted by blue signage and an M-prefixed or suffixed road number.
The construction and surfacing of motorways is generally of a higher standard than conventional roads, and maintenance is carried out more frequently; in particular, motorways drain water very quickly to reduce hydroplaning. The road surface is generally tarmac (“black top”) or concrete (“white top”). Other features are crash barriers, cat’s eyes and, increasingly, textured road markings (a similar concept to rumble-strips).
Common Criteria
For a road to be classified as motorway a number of conditions must be fulfilled. The following conditions generally apply:
· Accessed at junctions by slip roads off the sides of the main carriageway;
· Joined by link-roads at an interchange, the object of which is to allow traffic to change route without stopping or slowing significantly;
· Traffic lights are not permitted (except at toll booths and certain interchanges);
· Have signposted entry and exit points at the start and end;
· Certain types of transport are banned, typically pedestrians, bicycles, learner drivers, horses, agricultural vehicles, underpowered vehicles (e.g. small scooters, invalid carriages).
· Emergency telephones (which connect directly to the police) must be provided at a regular distance (in the UK emergency telephones are situated at intervals of 1 mile)
Speed Limits
Speed limits are generally higher than on ordinary roads. Some types of vehicle may be subject to a lower limit, while often sections of motorway are subject to lower speed limits due to local driving conditions.
In the UK the majority of motorways and dual carriageways have a maximum speed limit of 70 mph (113 km/h) for cars. In 2004 the Conservative Party proposed increasing the motorway speed limit to 80 mph (129 km/h) on some stretches. Some road safety groups feel this would be a good idea, as it more closely represents the normal (and, they claim, safe) driving practice of the majority of motorway users.
Many other roads are of near-motorway quality, but are not classified as such (generally for breaking one or more of the above rules). These are referred to as dual carriageways, which in Britain usually have the same 70 mph (113 km/h) limit.
Lane Usage
Diagram showing lanes and road layout
White dashed lines denote the lane separation, while an unbroken white line is painted alongside the median (usually known as the “central reservation”). A white line on the edge of the slow lane marks the edge of the hard shoulder. The hard shoulder is not used for traffic and is reserved for breakdowns or emergency maneuvers. Pedestrians should only use the hard shoulder to walk to emergency telephones and not for any other reason. Vehicles on the hard shoulder should activate their hazard warning lights.
Lanes closest to the edge of the road are intended for general driving – these are hence the “inside” lanes, while the lanes closest to the median are intended for overtaking (passing) slower-moving vehicles – hence they are termed “outside” lanes. Generally lanes closer to the centre of the road (outer lanes) are used for overtaking, while lanes near the edge of the road (inner lanes) are used for slower traffic. Under the Highway Code in the UK, it is not permitted to overtake on the left, except in emergencies, when signs indicate drivers may do so, or when traffic is moving slowly. Similar rules apply in Germany and some other countries.
Traffic should always use the left-hand-most lane as much as possible. Generally this means a vehicle should use the left-hand lane next to the hard shoulder, and use the other two lanes only for overtaking maneuvers, moving back into the left lane once they have passed the slower vehicle(s). In heavy traffic, it is acceptable to cruise in the middle lane to pass slower vehicles to avoid constant lane changes.
A significant problem on motorways is the “middle lane hog”, a driver who drives in the middle lane when there is no reason to do so. This can be very frustrating for other drivers. Faster vehicles approaching in the left hand lane have to maneuver across four lanes of the motorway rather than two to overtake such a vehicle, since undertaking is deemed dangerous. Drivers of heavy goods vehicles can be especially frustrated by a middle lane hog, as their vehicles are not permitted to use the right-hand-most lane on a three (or more) lane motorway under normal circumstances. Some vehicles try to convince a “right lane hog” to move to the slower lane by keeping a very close distance, which is also considered dangerous.
In the UK lanes in a given direction are numbered from left to right as lane 1, lane 2, lane 3, etc. Lane 1 is the lane next to the hard shoulder.
Junctions
The most basic motorway junction is a two-lane flyover with four slip-roads, two on each side of the motorway, to exit or enter. A simple crossroads or roundabout is present on either end of the flyover. A rather large version of a roundabout, using two curved flyovers is sometimes used to present a single large junction for users of the slip-roads or crossing road. The slip roads leading off the motorway are known as “exit slip roads”, those leading onto the motorway as “entry slip roads”. The precise slip road at any junction may be identified by reference to the direction of the carriageway, for example “northbound entry slip”.
The signal-controlled roundabout is often used in these situations and has become very common in Ireland. A far greater degree of complexity is present in Britain with varying types of Spaghetti Junction-style interchanges.
Location and Construction
Major intercity or national routes are often built or upgraded to motorway standard. Motorways are also commonly used for ring roads around cities or bypasses of built-up areas.
In Britain there are plans to improve many motorways as well as to upgrade some roads to motorway status. In Ireland, the National Roads Authority has been connecting main cities with motorways as part of a six-year National Development Plan. The European Union has part-funded many motorway projects in the past, as part of a Trans-European Transport Networks, and there are plans to invest billions of euros in such projects in the next ten years.
One of the most recently constructed motorways in the UK is the M6 Toll, bypassing Birmingham and Wolverhampton, which opened in 2004 and is the only completely toll motorway in England. There are tolled sections of motorway on the M4 and M48, where they cross the River Severn at the Severn crossings. Although the crossing of the River Thames east of London is tolled, the bridge and tunnels themselves are officially designated to permit usage by non-motorway traffic.
Unit 11 Freeway
This stylized drawing of an overpass is used to represent a freeway in many countries.
A freeway (also motorway or expressway) is a type of highway that is designed for safer high-speed operation of motor vehicles through the elimination of at-grade intersections. This is accomplished by imposing full control of access from adjacent properties and eliminating all cross traffic with grade separations and interchanges, and no railroad crossings. Such highways are usually divided with at least two lanes in each direction. Because traffic never crosses at-grade, there are generally no traffic lights or stop signs. The word freeway is also used to describe a highway without tolls.
Note: Expressway has other meanings, and motorway typically applies only to those roads designated as motorways by the national highway agency. Thus this article will primarily use the term freeway for clarity and conciseness. The terms “controlled access” and “limited access” are also used, but both terms can also apply to arterial roads with partial control of access.
Despite the name, a freeway can be a toll road.
General Characteristics
High-capacity freeway interchange in Los Angeles, California.
Freeways, by definition, have no cross traffic in the form of other roads and railroads. Elimination of cross traffic is typically achieved with grade separation using underpasses and overpasses. In addition to sidewalks attached to roads that cross a freeway, specialized pedestrian bridges or tunnels may also be provided. These structures enable pedestrians and cyclists to cross the freeway without a long detour to the nearest motor vehicle crossing. Movable bridges are occasionally present on freeways, requiring drivers to yield to river traffic.
Access is typically provided only at interchanges, though lower-standard right-in/right-out access can be used for direct connections to side roads or driveways to adjacent property. In ideal cases, sophisticated interchanges allow for smooth, uninterrupted transitions between intersecting freeways. However, sometimes it is necessary to exit onto a surface road to transfer from one freeway to another. Exits are sometimes numbered to help drivers identify their exit.
Two-lane freeways, often undivided, are sometimes built when traffic volumes are low or right-of-way is limited; they may be designed for easy conversion to one side of a four-lane freeway. Otherwise, freeways typically have at least two lanes in each direction; some busy ones can have as many as 16 lanes or up to 18 for short distances. These wide freeways may use separate collector and express lanes to separate through traffic from local traffic, or special high-occupancy vehicle lanes, either as a special restriction on the innermost lane or a separate roadway, to encourage carpooling. These HOV lanes, or roadways open to all traffic, can be reversible lanes, providing more capacity in the direction of heavy traffic, and reversing direction before traffic switches. Sometimes a collector/distributor road, a shorter version of a local lane, shifts weaving between closely-spaced interchanges to a separate roadway or altogether eliminates it.
Freeways can have frontage roads, normal surface roads parallel to and on either side of the freeway, to provide access to adjacent properties. Frontage roads typically have one-way traffic flow in urban areas and two-way traffic flow in rural areas.
Except on some two-lane freeways (and very rarely on wider freeways), a median separates the opposite directions of traffic. This strip may be as simple as a grassy area, or may include a crash barrier such as a Jersey barrier to prevent head-on collisions. On some freeways, the two carriageways are built on different alignments; this may be done to make use of available corridors in a mountainous area or to provide narrower corridors through dense urban areas.
Speed limits are generally higher than on similar non-freeways, and are sometimes nonexistent. Because the high speeds reduce decision time, freeways are usually equipped with a larger number of guide signs than other roads, and the signs themselves are physically larger. In major cities, guide signs are often mounted on overpasses or overhead gantries so that drivers can see where each lane goes.
In most parts of the world, there are public rest areas or service areas on freeways. Many countries also provide emergency phones alongside freeways at regular intervals.
To reduce the probability that high-speed freeway traffic will have to slow down for slower same-direction traffic, access to freeways is usually limited to classes of motor vehicles that are powerful enough to maintain a certain minimum speed. Some countries partially restrict the use of motorcycles or ban them completely from freeways.
Effects and Controversy
Rush hour on I-45, downtown Houston.
Freeways have been constructed both between urban centres and within them, making common the style of sprawling suburban development found near most modern cities. As well as reducing travel times, the ease of driving on them reduces accident rates, though the speeds involved also tend to increase the severity and death rate of the collisions that do still happen.
Freeways have been heavily criticized by environmentalists and preservationists for the noise, pollution, and economic shifts they bring. Additionally, they have also been criticized by the driving public for the inefficiency with which they handle peak hour traffic.
Often, rural freeways open up vast areas to economic development, generally raising property values. But mature freeways in urban areas are quite often a source of lowered property values, contributing to the deleterious effects of urban blight. One major problem is that even with overpasses and underpasses, freeways tend to divide neighborhoods — especially impoverished ones where residents are less likely to own a car that could easily take them around the freeway. For these reasons, almost no new urban freeways have been built in the U.S. since 1970.
Some have even been demolished and reclaimed as boulevards, notably in Portland (Harbor Drive), San Francisco (Embarcadero Freeway) and Milwaukee (Park East Freeway). Growing anti-urban freeway sentiment has resulted in some significant policy changes; the most noteworthy was an FHWA case study involving the West Side Highway in Manhattan, a quintessential urban freeway in need of expansion and reconstruction. The outcome of the study basically concluded that the current elevated highway should be replaced with a new, at-grade boulevard with integrated pedestrian facilities. This case study may be a precedent for areas where a typical, elevated urban freeway is not desirable and/or may not be effective at handling impacted traffic. In Boston, Massachusetts, the elevated Central Artery, originally built in the 1950s, was demolished in 2005 when new tunnels were built for an expanded Central Artery directly beneath the pre-existing elevated highway. Completion of the project, referred to as the Big Dig allowed Boston to reunite its business district with the waterfront, severed by the original elevated Central Artery, while maintaining the expressway through downtown, now located underground.
Freeway opponents argue that freeway expansion is self-defeating, in that expansion will just generate more traffic. That is, even if traffic congestion is initially shifted from local streets to a new or widened freeway, people will begin to run errands and commutes to more remote locations which took too long to reach in the past. Over time, the freeway and its environs will become congested again as both the average number and distance of trips increase.
Freeway advocates argue that properly designed and maintained freeways are aesthetically pleasing, convenient, and safe, at least in comparison to the uncontrolled roads they replace or supplement, and that they expand recreation, employment and education opportunities for individuals and open new markets to small businesses. And for many, uncongested freeways are fun to drive.
At present, freeway expansion has largely stalled in the United States, due to a multitude of factors that converged in the 1970s: higher due process requirements prior to taking of private property, increasing land values, increasing costs for construction materials, local opposition to new freeways in urban cores, the passage of the National Environmental Policy Act which imposed the requirement that each new project must have an environmental impact statement or report.
History
The concept of limited-access automobile highways dates back to the New York City area Parkway system, whose construction began in 1907–1908; but parkways are traditionally distinguished from freeways by lower design speeds and a ban on commercial traffic. Designers elsewhere also researched similar ideas, especially in Germany, where the Autobahn would become the first national freeway system.
However, in 1925, Italy was technically the first country to build a freeway, which linked Milan to Lake Como. It is known in Italy as the Autostrada dei Laghi.
Meanwhile, in England, the related concept of the motorway was first proposed by Sidney Webb in a 1910 book “The King's Highway” but was not formally embraced by the government until the passage of the Special Roads Act 1949. In 1926, the English intellectual Hillarie Belloc recognized the necessity of grade-separated roads for “rapid and heavy traffic”, but thought they would be the exception rather than the rule: “The creation of a great network of local highways suitable for rapid and heavy traffic is impossible. Even if the wealth of the community increases, the thing would be impossible, because it would mean the destruction of such a proportion of buildings as would dislocate all social life.”
The word “freeway” first surfaced in the mid-1930s in proposals for the improvement of the New York City parkway network.
The first long-distance rural freeway in the United States is generally considered to be the Pennsylvania Turnpike, which opened on October 1, 1940. The Turnpike was so advanced for its time that tourists even had picnics in the median (that is, after it was already open to traffic) and local entrepreneurs did a brisk business in souvenirs. It was designed so that straightaways could handle maximum speeds of 102 miles per hour, and curves could be taken as fast as 90.
Shortly thereafter, on December 30, 1940, California opened its first freeway, the Arroyo Seco Parkway (now called the Pasadena Freeway) which connected Pasadena with Los Angeles. And in 1942, Detroit, Michigan opened the world's first urban depressed freeway, the Davison Freeway. Meanwhile, traffic in Los Angeles continued to deteriorate and local officials began planning the huge freeway network for which the city is now famous.
Recent Developments
Outside the U.S., many countries continue to rapidly expand their freeway networks. Examples include: Australia, Canada, Chile, China, Croatia, France, India, Israel, Mexico, Malaysia, Pakistan, the Philippines, Spain and Taiwan. Australia and France in particular have been innovative in using the newest tunneling technologies to bring freeways into high-density downtowns (Sydney and Melbourne) and historic rural areas (Versailles). China already has the world's second largest freeway network in terms of total kilometers and will probably overtake the U.S. well before 2025.
In Australia, the city of Adelaide pioneered the concept of a dedicated reversible freeway. The M2 expressway runs toward the city in the morning and out of the city in the evening. Its ramps are designed so that they can double as on- or off-ramps, depending upon the time of day. Gates and electronic signage prevent motorists from driving in the wrong direction.
Meanwhile, major progress has been made in making existing U.S. freeways and expressways more efficient. Experiments include the addition of high-occupancy vehicle lanes (HOV lanes) to discourage driving solo, and building new roads with train tracks down the median (or overhead). California’s Caltrans has been very innovative in squeezing HOVs into limited right-of-way (by elevating them), and in building special HOV-only ramps so that HOVs can switch freeways or exit the freeway without having to merge across regular traffic. Many states have added truck-only ramps or lanes on heavily congested routes, so that cars need not weave around slow-moving big rigs.
Intelligent transportation systems (ITS) are also increasingly used, with cameras to monitor and direct traffic, so that police, fire, ambulance, tow, or other assistance vehicles can be dispatched as soon as there is a problem, and to warn drivers via variable message signs, radio, television, and the web to avoid problem areas. Research has been underway for many years on how to partly automate cars by making smart roads with such things as buried magnets to guide sensor-equipped vehicles, with on-board GPS to determine location, direction, and destination. While these systems may eventually be used on surface streets as well, they are most practical in a freeway setting.
Unit 12 Autobahn
The German autobahn sign
Autobahn is the German word for a major high-speed road restricted to motor vehicles and having full control of access, similar to a motorway or freeway in English-speaking countries.
In most countries, it usually refers to the German Autobahn specifically. German autobahns have no general speed limit, but the “recommended speed” is 130 km/h (80 mph). Austrian and Swiss autobahns have general speed limits of 130 km/h and 120 km/h (75 mph), respectively. In German, the word is pronounced as described above, and its plural is Autobahnen; in English, however, the segment “auto” is typically pronounced as in other English words such as “automobile”. The official name of the Autobahn in Germany is Bundesautobahn (BAB) (federal motorway).
Construction
Similar to such freeways in other countries, autobahns have multiple lanes of traffic in each direction, separated by a central barrier with grade-separated junctions and access restricted to certain types of motor vehicles only. The first German Autobahn was completed in 1932 between Cologne and Bonn (it was the world’s very first motorway!). Each carriageway was flanked by bankettes about 60 cm (2 ft) in width, constructed of varying materials; right-hand bankettes on many autobahns were later retrofitted to 120 cm (4 ft) in width when it was realized cars needed the additional space to pull off the autobahn safely. In the postwar years, a thicker asphaltic concrete cross-section with full paved hard shoulders came into general use. The top design speed was approximately 160 km/h (100 mph) in flat country but lower design speeds could be used in hilly or mountainous terrain. A flat-country autobahn constructed to published design standards in use during the Nazi period could support hands-off speeds on curves of about 150 km/h (95 mph).
The number signet for the “A 8” as it appears on all traffic signs
The current autobahn numbering system in use in Germany was introduced in 1974. All autobahns are named by using the capital letter “A” followed by a blank and a number (for example “A 8”). The “main autobahns” going all across Germany have a single digit number usually even-numbered for east-west routes and odd-numbered for north-south routes. Some roads may not be as easily distinguished as strictly either as it would be, for example, in the United States whose major roads follow routes that are clearly horizontal or vertical when viewed on a conventional map. Shorter autobahns that are of regional importance (e.g. connecting two major cities or regions within Germany) have a double digit number (e.g. A 24, connecting Berlin and Hamburg).
There are also very short autobahns of just local importance (e.g. beltways or the A 555 from Cologne to Bonn) that usually have three numbers the first one of which is similar to the system above, depending on the region.
History
A German autobahn in the 1930s The two-lane autobahn, with no
emergency lane (Germany)
The idea for the construction of the Autobahn was first conceived during the days of the Weimar Republic, but apart from the AVUS in Berlin, construction was slow, and most projected sections did not progress much beyond the planning stage due to economic problems and a lack of political support. One project was the private initiative HaFraBa which planned a “car-only road” (the name autobahn was created in 1929) crossing Germany from Hamburg in the North via central Frankfurt am Main to Basel in Switzerland. Parts of the HaFraBa were completed in the 1930s and early 1940s, but construction eventually was halted by World War II.
Just days after the 1933 Nazi takeover, Adolf Hitler enthusiastically embraced an ambitious autobahn construction project and appointed Fritz Todt the Inspector General of German Road Construction. Soon, over 100,000 laborers worked at construction sites all over Germany. As well as providing employment and improved infrastructure, necessary for economic recovery efforts, the project was also a great success for propaganda purposes. It has been said that another aim of the autobahn project, beyond creating national unity and strengthening centralized rule, was to provide mobility for the movement of military forces. This, however, overlooks the fact that gradients on autobahns built before the war were far too steep for the goods vehicles of the time. The autobahn’s main purpose, then, was to enable a large proportion of the population to drive long distances in their own cars, enjoying the countryside along the way. This explains some of the autobahn’s routing which offers spectacular views but is impractical for today’s heavy goods traffic.
The autobahns formed the first limited-access, high-speed road network in the world, with the first section from Frankfurt am Main to Darmstadt opening in 1935. This straight section was used for high speed record attempts by the Grand Prix racing teams of Mercedes-Benz and Auto Union until a fatal accident involving popular German race driver Bernd Rosemeyer in early 1938. A similar high speed section was built between Dessau and Halle.
During World War II, the central reservations of some autobahns were paved to allow their conversion into auxiliary airports. Aircraft were either stashed in numerous tunnels or camouflaged in nearby woods. However, for the most part, the autobahns were not militarily significant. Motor vehicles could not carry goods as quickly or in as much bulk as trains could, and the autobahns could not be used by tanks as their weight and caterpillar tracks tore up the roads’ delicate surfaces. Furthermore, the general shortage of gasoline which Germany experienced during much of the war, as well as the relatively low number of trucks and motor vehicles badly needed for direct support of military operations, further decreased the attractiveness of autobahns for significant transport. As a result, most military and economic freight continued to be carried by rail. After the war, numerous sections of the autobahns were in bad shape, severely damaged by heavy Allied bombing and military demolition. As well, thousands of kilometers of autobahns remained unfinished, their construction brought to a halt by 1943 due to the increasing demands of the war effort.
In West Germany, following the war, most existing autobahns were soon repaired. During the 1950s, the West German government restarted the construction program; it continuously invested in new sections and in improvements to older ones. The finishing of the incomplete sections took longer, with some stretches being opened to traffic only in the 1980s. Some sections cut by the Iron Curtain in 1945 were only completed after German reunification in 1990. Finally, certain sections were never completed, as more advantageous routes were found. Some of these sections stretch across the landscape forming a unique type of modern ruin, often easily visible on satellite photographs.
The autobahns in East Germany (GDR) and the former German provinces of East Prussia, eastern Pomerania and Silesia in Poland and the Soviet Union after 1945 were grossly neglected in comparison to those in West Germany and Western Europe in general. They received minimal maintenance during the years of the Cold War. The speed limit on the GDR autobahns was 100 km/h (62 mph), however lower speed limits were frequently encountered due to the poor condition of the road surface, changing quickly in some instances. The speed limits on the GDR autobahns were rigorously enforced by the Volkspolizei, whose patrol cars were frequently encountered hiding under camouflage waiting for speeders. In the 1970s and 80s, the West German government paid millions of Deutsche Marks to the GDR for construction and maintenance of the transit autobahns between West Germany and West Berlin, although there were indications that the GDR diverted some of the earmarked maintenance funds for other purposes.
Current Density
Map of the German autobahn network
Today, Germany’s autobahn network has a total length of about 11,980 km. Many sections of Germany’s autobahns are modern, containing three lanes in addition to an emergency lane. Some other sections remain in their original state, with two lanes, no emergency lane, short ramps, etc. Such a combination of the two types of autobahn can be seen on the A 9 autobahn (Munich-Berlin). Heading out from Munich, the autobahn starts off as a modern, four-lane in each direction + emergency lane autobahn. However, after heading into Thuringia, which was formerly part of East Germany, parts of the autobahn are no wider than two lanes and no emergency lane exists (only rare emergency bays with a telephone post in orange-yellow). Ongoing roadworks will eventually bring the entire A 9 to three-lane standard.
Speed limits
The German autobahns are famous for being some of the few public roads in the world without blanket speed limits for cars and motorcycles. Lack of blanket speed limits does not appear to negatively impact the road safety of autobahns compared with motorways in other countries; motorways are safer than other road types. Certainly, speed limits do apply at junctions and other danger points, like sections under construction or in need of repair. Certain stretches have separate, and lower, speed limits used in cases of wet lanes.
Some limits were imposed to reduce pollution and noise. Limits can also be put into place temporarily through dynamic traffic guidance systems that display the according traffic signs. If there is no speed limit, the recommended speed limit is 130 km/h (81 mph); this speed is not a binding limit, but being involved in an accident at higher speeds can lead to being deemed at least partially responsible due to “increased operating danger”. The average rate of speed traveled on the autobahn in unregulated areas by automobiles not regulated by other laws is about 150 Km/h (93 mph). On average, about half of the total length of the German autobahn network has no speed limit, about one third has a permanent limit, and the remaining parts have a temporary limit for a number of reasons.
In places without a general limit, there are mostly also no restrictions on overtaking. Therefore, those traveling at high speeds may regularily encounter trucks running side-by-side at only about 80 km/h (50 mph). In theory, trucks are not allowed to overtake others unless they drive 20 km/h (12 mph) faster than whomever they are overtaking, but truck drivers are generally under pressure to arrive in time, and such laws are rarely enforced for economic and political reasons, as many trucks are from foreign countries. The right lane of a typical autobahn is often crowded with trucks, and too often, trucks pull out to overtake. Due to size and speed this is often referred to as “Elephant Race”. In some zones with only two lanes in both directions there is no speed limit, but a special overtaking restriction for trucks and/or cars pulling trailers.
Modern cars easily reach well over 200 km/h (124 mph), and most large car manufacturers follow a gentlemen’s agreement by artificially limiting the top speed of their cars to 250 km/h (155 mph) for safety reasons (inexperienced drivers and risk of tires failing, especially when underinflated). Yet, these limiters can easily be defeated, so speeds exceeding 300 km/h (186 mph) are not unheard of, although due to common speed limits and other traffic, such speeds are rarely attainable.
Vehicles unable to attain speeds in excess of 60 km/h (37 mph) are not allowed to use the autobahn. Though this limit is not high for most modern vehicles, it prevents very small cars (e.g. Quads) and motor-scooters (e.g. Mofas) from using autobahns. To comply with this limit, several heavy-duty trucks in Germany (e.g. for carrying tanks or cranes) have a design speed of 62 km/h (usually denoted by a round black-on-white sign with “62” on it).
Since the mid-1980s, when environmental issues gained importance and recognition among lawmakers, interest groups and the general public, there has been an ongoing debate on whether or not a nationwide general speed limit should be imposed for Autobahns. Obviously, a car’s fuel consumption increases with speed, and fuel conservation is a key factor in reducing pollution. Safety issues have been cited as well with regards to speed-related fatalities. Opposers of a general speed limit maintain that such regulation is unnecessary because only two percent of all German roads would be affected and because better fuel economy even at high speeds has been achieved in most modern cars. Moreover, recent accident statistics supposedly don't lend proof that traveling at high speeds is that much more dangerous.
Twenty years after the beginning of this debate, there are still no definite plans by the federal government concerning such a speed limit.