Caution is required when approaching discussions of the topic. Some of the claims and counter-claims regarding cycle facilities might be best interpreted as competing ideological doctrines rather than established engineering truths. The arguments have also been characterised in terms of a social custom or a taboo that reserves the roadway for motorised users.
The use of segregated facilities has been a source of a great deal of controversy since the 1930s. Some commentators inaccurately use various terms interchangeably. In some cases this is done out of simple ignorance but in other cases this may result from deliberate attempts to confuse matters that involve serious accusations related to fatality, injury and legal culpability. Even the use of the word "facility" is controversial and is disputed.
While the names and definitions of the various cycle facility types vary from country to country, they essentially fall into two categories: "On-road" and "Off-road".
"Off-road" types may be on their own dedicated right-of-way or run alongside a road. In the USA, off-road unsurfaced trails are commonly called "bike trails" or "mountain-bike trails", while surfaced trails that are separate from roadways and that meet more rigorous standards for width, grade and accessibility are commonly called "bike paths." In the UK and some other jurisdictions, the terms "cycle path" or "cycle track" are sometimes used as a blanket term for any such off-road facility.
This article observes the following conventions.
An example of an early segregated cycle facility was the nine-mile dedicated Cycle-Way built in 1897 to connect Pasadena, California to Los Angeles. Its right of way followed the stream bed of the Arroyo Seco and required 1,250,000 board feet (2,950 m³) of pine to construct. The roundtrip toll was US$.15 and it was lit with electric lights along its entire length. The route did not succeed, and the right of way later became the route for the Arroyo Seco Parkway, an automobile freeway opened in 1940.
Post-war German governments chose to continue the transportation objectives of their Nazi predecessors, and cyclists were viewed as an impediment to motorised traffic to be excluded and restricted whenever feasible . By the end of the 1960s Germany's transport policies had caused cycling to fall from 50% to 5% of trips. In the UK, little use of separate cycleway/cycle track systems took place except in the so-called "new towns" such as Stevenage and Harlow. From the end of the 1960s in Nordic countries, the Swedish SCAFT guidelines on urban planning were highly influential and argued that non-motorised traffic must be segregated from motorised traffic wherever possible. Under the influence of these guidelines cyclists and pedestrians were treated as a homogeneous group to be catered for using similar facilities. The guidelines strongly influenced cities such as Helsinki and Västerås to build large cycle path networks. By the late 1960s and 1970s, with the cyclists mainly gone, many German towns began removing cycle tracks so as to accommodate more car parking. Increasing traffic congestion and the 1970s oil shocks contributed to a resurgence in cycling in some countries. Outside of SCAFT-inspired developments in Nordic countries, the use of segregated cycle facilities was mainly confined to university towns with established populations of bicycle users.
Since the 1930s, the established cycling lobby in the UK and Ireland has taken a critical and measured view of the utility and value of segregating cyclists. In 1947, in response to official suggestions that cyclists should use cycle-tracks, the CTC adopted a motion expressing determined opposition to cycle paths alongside public roads. In 2007, official claims of safety for cycle tracks provoked a position paper from the umbrella body for UK cyclists' groups, stating "Cycle Campaign Network knows of no evidence that cycle facilities and in particular cycle lanes, generally lead to safer conditions for cycling" .
In the 1970s the California Statewide Bicycle Committee arranged with Kenneth D. Cross for a study of car-bike collisions, expecting that this study would support their arguments on collision prevention. When presented to the Committee in Sacramento on June 19 1974, Cross's study showed the opposite: only 0.5% of car-bike collisions had occurred between straight-ahead cyclists and overtaking straight-ahead motorists. Cross later had a contract with the National Highway Traffic Safety Administration (NHTSA) to produce an improved study (on a pseudo-random national sample), and the results were much the same. A 2006 report concludes that "bicycle safety data are difficult to analyse, mostly because bicycle trip data (and thus accident probability per trip) are hard to uncover" (see NCHRP Report 552, 2006, "Guidelines for Analysis of Investment in Bicycle Facilities", National Cooperative Highway Research Program, Transportation research Board of the National Academies, page F-1). The Netherlands and Denmark, which have the highest rates of cycle usage combined with the best records for safety, used to give their segregated cycle path networks primary importance in achieving these goals. However, the largest study undertaken into the safety of Danish cycle facilities has found that safety has decreased as a result. More recently, Shared Space redesigns of urban streets in those and other countries have achieved significant improvements in safety (as well as congestion and quality of life) by replacing segregated facilities with integrated space.
For urban roads with many junctions, accident analysis suggests that segregated cycling facilities are likely to produce a net increase in the number of collisions. These conclusions are supported by the experience of countries that have implemented segregated cycling facilities. In the U.S., UK, Germany, Sweden, Denmarkand Finland, it has been found that cycling on roadside urban cycle tracks/sidepaths results in up to 12-fold increases in the rate of car/bicycle collisions. At a 1990 European conference on cycling, the term Russian roulette was used to describe the use of roadside cycle paths.
In Helsinki, research has shown that cyclists are safer cycling on roads with traffic than when using the city's 800 km of cycle paths . The Berlin police and Senate conducted studies which led to a similar conclusion in the 1980s . In Berlin 10% of the roads have cycle paths, but these produce 75% of fatalities and serious injuries among cyclists . In the English town of Milton Keynes it has been shown that cyclists using the off-road Milton Keynes redway system have on a per-journey basis a significantly higher rate of fatal car-bicycle collisions than cyclists on ordinary roads. Cycle lanes and bike lanes are less dangerous than cycle paths in urban situations but even well-implemented examples have been associated with 10% increases in casualty rates.
Particular concern attaches to the use of cycle lanes in urban situations such as large roundabouts. For adults, the standard safe cycling advice for handling roundabouts is to try to maintain a prominent position while circulating . The use of cycle lanes runs counter to this advice and places cyclists outside the main "zone of observation" of entering motorists, who represent the overwhelming source of risk (50% of collisions) . In 2002, cycle lanes were removed from a roundabout in the English town of Weymouth after 20 months because the casualty rate had increased significantly . German research has indicated that cyclists are safer negotiating roundabouts in traffic rather than on separate cycle lanes or cycle paths . A recent paper on German roundabout design practice states "Cycle lanes at the peripheral margin of the circle are not allowed since they are very dangerous to cyclists". See also cycle facilities at roundabouts.
Direct rear impacts with cyclists are a more prominent collision type in arterial/rural road type situations. When they occur in such circumstances they are also associated with significantly increased risk of fatality. Data collated by the OECD indicates that rural locations account for 35% or more of cycling fatalities in Denmark, Finland, France, Great Britain, Japan, the Netherlands and Spain.
Cycling collision data recorded by police in the UK data indicates that at non-junction locations, where a cyclist was struck directly from behind there was an overall fatality rate of 17%. The rate of fatality increases with speed limit of the road: 5% on 30 mph roads, 13% on 40 mph, 21% on 60 mph and 31% on 70 mph roads.
The use of appropriately designed segregated space on arterial or interurban routes appears to be associated with reductions in overall risk. In Ireland, the provision of hard shoulders on interurban routes in the 1970s reportedly resulted in a 50% decrease in accidents. It is reported that the Danes have also found that separate cycle tracks lead to a reduction in rural collisions.
The "safety in numbers" argument has also been used to explain the apparent success of cycle facilities in some cities. In most cases, the most prominent examples of "successful" cycle networks were implemented in towns that already had significant numbers of cyclists. It is argued that in such cases this existing large cycling population already exerts a strong "safety in numbers" effect, and it is this, rather than their diversion onto off-road tracks that accounts for the higher safety seen. More people might start cycling if the perceived safety of doing so improved sufficiently. Segregated cycle facilities are one way to improve the perception of safety. There are other approaches, such as Shared Space, which improve actual safety in part by decreasing the difference between real and perceived safety. See the Utility cycling article for other examples of measures to improve both actual and perceived safety.
Various remedial measures have been developed in an attempt to solve the identified safety problems of segregated cycle facilities. In some environments these represent established engineering practice while in others they may have to be retroactively applied in response to complaints and safety concerns. Examples include the addition of a separate system of traffic signals for bicycle traffic. This can get extremely complex, particularly if there are already separate traffic signal phases for pedestrians, motorised traffic and public transport.
The need for a separate system of traffic lights also means that building a functioning completely segregated cycle path system is a non-trivial exercise in terms of both expense and engineering effort. Some treatments involve raising the cycle track onto a speed ramp type structure where it crosses side roads. In addition, various road markings have been developed in an attempt to remedy the issue of increased junction collisions. Examples of these include the use of special road markings, e.g. "sharks teeth" or "elephants footprints", and treatments using red, green or blue coloured tarmac. When such treatments are implemented retroactively they are often proclaimed as safety "improvements" However, cycle-facility sceptics view such claims as, at best, disingenuous. They argue that in many cases the actual purpose is to "restore" the level of safety that existed before the marking/construction of the segregated cycle facility.
An associated approach may be to "traffic calm" the bicycle traffic by introducing tight curves or bends to slow the cyclists down as they near a junction. Alternatively, traffic engineers may remove priority from the cyclists and require them to yield to turning traffic at every side road. In 2002, engineers proposing a sidepath scheme in the Irish university city of Galway stated that cyclists would be required to dismount and "become pedestrians" at every junction on the finished route.
One of the potential pitfalls for observers trying to interpret the operation of segregated cycle facilities is that the same legal assumptions do not apply in all environments. For instance, in contrast to most English speaking countries, some Northern European countries, including Germany, France, Denmark, Belgium and the Netherlands have defined liability legislation. Thus there is a legal assumption that motorists are automatically considered liable in law for any injuries that occur if they collide with a cyclist. This may hold regardless of any fault on the part of the cyclist and may significantly affect the behaviour of motorists when they encounter cyclists. In some countries it is legal for cyclists to overtake motor-vehicles on the inside, and cyclists doing so may enjoy the protection of the law. In this case, the use of segregated cycle facilities conforms to existing traffic law. In other jurisdictions similar "undertaking" manoeuvres by cyclists are illegal. Such distinctions form the basis of the argument that segregated cycle facilities encourage behaviours that flout existing traffic law and in which cyclists enjoy no legal protection.
This variation also applies to the operation of traffic signals and cyclist-specific traffic lights. For instance, in Germany and elsewhere at junctions with segregated facilities all the traffic in a given direction (motorists, pedestrians and cyclists) may get a green signal at the same time. Turning motor traffic is obliged to wait for cyclists and pedestrians to clear the junction before proceeding. In this situation all the transport modes get equal green time. In contrast, UK and Irish practice restricts pedestrians to a dedicated signal phase, separate from and usually much shorter than the green phase for motorists (e.g. 6-12 seconds, vs. signal cycle times of up to 120 seconds). If cyclists were to be segregated and treated in a similar manner this would imply a significant reduction in green time for cycle traffic at every junction. In the English city of Cambridge the use of cyclist-specific traffic signals is reported to have resulted in increased delays for cyclists, leading some to ignore the cycle-facilities and stay on the road. A similar example occurred in a Parisian bikepath scheme in 1999. Cyclists faced twice the number of traffic signals as motorised traffic and were expected to wait over one minute to get seven seconds of green time. Conversely, in Copenhagen cyclist-specific traffic signals on a major arterial bike lane have been linked to provide "green waves" for rush hour cycle-traffic.
Other potential pitfalls in interpreting the operation of segregated cycle facilities are the issues of design vehicles and design users. The Netherlands is a flat country and Dutch town planning keeps cycling distances short. The typical Dutch town bike or "granny bike" has no gears or a three-speed hub gear and back pedal brakes. In countries with different geographies and cycling cultures bicycles tend to have 7-15 gears (not counting duplicates), and a reasonably fit adult commuter can expect to reach speeds of 30 km/h (20 mph) Sports cyclists can travel even faster: with tailwinds or downhill gradients, some cyclists may exceed 50 km/h (30 mph). While a Dutch sidepath system may work for Dutch cyclists, serious questions have been raised since at least the 1970s that other cyclists using faster bicycle types cannot use such a system safely at their higher normal cycling speeds. The Danish Roads Directorate acknowledges that the advent of faster bicycle types has not increased safety, since their cycle track system "functions best when cyclists travel at relatively low speeds"
In some cases designers may focus on a particular design user. The UK’s Sustrans guidelines for the National Cycle Network are based on recreational use with a design user who is an unaccompanied 12-year-old. The Dublin Transportation Office has advertised their cycle facilities as being based on an unaccompanied ten-year-old design user. This raises the issue of what happens if different cyclist types find themselves forced onto such devices either by legal coercion or as a result of motorist aggression. This issue is captured in a 1996 review of the Sustrans approach from the Proceedings of the Institution of Civil Engineers. "The fast cycle commuter must not be driven off the highway onto a route that is designed for a 12-year-old or a novice on a leisure trip, because if that happens, the whole attempt to enlarge the use of the bicycle will have failed "
Moving motor vehicles generate a "sweeping" effect that pushes debris such as grit and broken glass to the edge of the roadway. By excluding motor traffic, cycle lanes and cycle tracks become parts of the road that are no longer routinely "swept", thus collecting more broken glass and gravel. In addition, some off-road designs are simply not accessible to standard road sweeping equipment. One UK study estimated that cycle path users are seven times more likely to get punctures than are road cyclists. Both sides of the argument acknowledge that many cyclists will simply refuse to use poorly maintained facilities. Cycle facilities skeptics go further and argue that there is no point funding new cycle facilities unless there is a simultaneous commitment of increased funds to maintenance and sweeping afterwards. Similar problems arise in areas subject to high leaffall in autumn, or high snowfall in winter, any cycle facilities must be subject to regular clearing or else rapidly become unusable. Danish guidance specifies three different categories of cycle track. Category "A" tracks must be kept clear of snow 24 hours a day, category "B" tracks are swept or cleared daily, and category "C" receive less regular winter maintenance. In 2007 the city of Copenhagen spends DKK 9.9 million (US$1.72 million, EUR1.33 million) annually on maintaining its cycle track network . German federal law requires local authorities to declassify cycle tracks that do not conform to strict design and maintenance criteria.
There is well-established historical precedent for the use of cycle facilities as a means of promoting motoring at the expense of cyclists. Despite this, some commentators, particularly those associated with the environmental and/or motoring lobbies, proclaim segregated cycle facilities as the "measure of choice" for restoring cyclist access to western cities. This is highly controversial and is a source of dispute, occasionally quite bitter - see also cycle path debate.
In contrast, in 1996 the CTC and the Institute of Highways and Transportation jointly produced a set of Cycle-Friendly Infrastructure guidelines that placed segregated cycling facilities at the bottom of the hierarchy of measures designed to promote cycling. Planners at the Directorate Infrastructure Traffic and Transport in Amsterdam place cyclists and motorists together on roads with speed limits at or below 30 km/h, and segregate them through bicycle lanes at higher limits. This is in a context where most of the measures prioritised by Cycle-Friendly Infrastructure (HGV restrictions, area-wide traffic calming, speed limit enforcement etc) are already in place - see Utility cycling for more detail.
A key criticism made by the opponents of such schemes is that the focus is often on constructing "cycle facilities" rather than "facilitating cyclists". It is readily apparent that there are many cities that have extensive cycle networks and also high levels of cycling. However, the most prominent examples tend to be compact, often mediaeval, university cities. This common theme has been taken to suggest that other underlying factors are driving the levels of cycle use.
Some commentators argue that the "cause and effect" being seen is actually the reverse of that which is often claimed: that it is the presence of large numbers of cyclists that tends to precipitate the construction of segregated cycle facilities. For instance, bike planning in Davis, California was driven by the prior existence of a "dramatic volume" of cyclists in the 1960s. Possibly the best that can be said is that the safety of cycling and the number of cyclists results from a complex interaction of spatial planning, population density, legislative environment, and wider traffic/transportation management policies. The evidence suggests that segregated cycle facilities can play either a positive or negative role, secondary to other factors - see utility cycling.
Separate cycleways and bike trails are less controversial when used to promoting recreational cycling. In Northern European countries, cycling tourism represents a significant proportion of overall tourist activity. Extensive interurban cycleway networks can be found in countries such as Denmark, which has had a national system of cycle routes since 1993. These may use roads dedicated to exclusively cycle traffic or minor rural roads whose use is otherwise restricted to local motor traffic and agricultural machinery. The UK has recently implemented the National Cycle Network.
Where available these routes often make use of abandoned railway corridors - see picture right of Mosel Maar cycle route. A prominent example in the UK is the Bristol & Bath Railway Path, a off-road cycleway that is part of National Cycle Route 4. Other UK examples include The Ebury Way Cycle Path, The Alban Way, the Hillend Loch Railway Path and the Nicky Line. In 2003 the longest continuous cycleway in Europe was opened, along the Albacete-Valdeganga highway in Spain, a distance of 22 km . Bogota's Bike Paths Network or "Ciclo-Ruta" in Spanish, designed and built during the administration of Mayor Enrique Peñalosa attracts significant recreational use.
In terms of multi-use trails, a "shared trail" may refer to a shared trail corridor with or without segregation within the corridor. In this context, segregated cycle facilities are a subset of shared facilities. Segregation may be supported by physical separation.