This chapter is meant to cover safety while riding a bicycle on a road. For more information on general safety, including preparing for riding, please see the General Safety chapter.
Bicycle crashes 
The first recorded bicycle accident is probably a collision in 1842, allegedly between Kirkpatrick McMillan, an early rider of the velocipede, and a young girl in Glasgow. The report, however, is vague and the identification disputed.
Causes of crashes vary according to local conditions. Research in the UK, based on hospital based samples, has found that 72% of cyclist accidents involved no other vehicle at all, and that 7% were claimed to be caused by motor vehicles. This contrasts with another analysis which found that between 60% and 85% of serious cyclist injuries are the result of negligence by a motor driver. A study conducted in 2000 by SWOV (Institute for Road Safety Research) in the Netherlands found that single bicycle accidents accounted for 47% of all bicycle accidents, collisions with obstacles and animals accounted for 12%, and collisions with other road users accounted for 40% (with the remaining 1% having unknown or unclassified cause).
This is what one would expect from thermodynamics; a cyclist only accident only provides a small amount of energy whereas a motor vehicle can provide a lot. The injuries are related to the energy available. Falling off and hitting obstructions tend to be relatively minor, usually not involving any hospital attention, so no appearance in the statistics. Motor vehicles add a lot of energy; even at very low speeds they can crush cyclists.
Defining danger 
The boundaries are blurred due to cyclists' reputation for flouting the rules of the road. Some of this is deserved, some is not. In its Research Report 549 of 2003, the Transport Research Laboratory noted that:
A key finding which should be noted was that, when commenting on the scenarios it was usually the behaviour of the cyclist that was criticised – no matter how small the misdemeanour. Few links were made between the cyclist’s behaviour and any external influences that could be affecting their choice of behaviour; i.e. the respondents’ comments indicated that they thought the cyclist’s actions were inherent and dispositional behaviours. In contrast, the motorists’ misdemeanours were excused or justified in terms of the situational influences. As this tendency seemed to continue across the groups and the individual depth interviews and was unprompted, it is unlikely that group dynamics had any significant effect on this finding. [...] This aligns with the psychological prediction of targeting of members of an ‘out group’.
Defining safety 
Although many accidents involve a cyclist alone, collisions whether accidental or not that also involve a motor vehicle put a cyclist in much greater danger and therefore account for a much greater number of serious injuries. A cyclist who is hit by a car is more likely to be killed than one who just falls off.
As long ago as the early 1930s there were efforts to clear cyclists off the roads to make way for private cars, then the preserve of the elite. These were successful in Germany, then an authoritarian regime, and spread during the war to German-occupied countries such as the Netherlands, but was resisted in other countries.
During the mid-part of the twentieth century, the traffic engineering response to the increased use of motor vehicles in the United Kingdom, as in the rest of the industrialised world, was to look for solutions which not only eased the passage of traffic through the streets, but which also protected vulnerable road users from the dangers of the motor car. In the 1940s, an influential proponent of this ideology was Herbert Alker Tripp, an assistant commissioner of London's Metropolitan Police. Tripp argued in his book Town Planning and Road Traffic that: "If we could segregate pedestrians completely from the wheeled traffic, we could of course abolish pedestrian casualties". This philosophy was also pursued by Colin Buchanan, his 1963 report for the UK Government Traffic in Towns, defined future government policy until the end of the century. Buchanan himself knew that segregation had not been proven to work in the case of cyclists, he famously wrote in his 1958 book Mixed Blessing "The meagre efforts made to separate cyclists from motor traffic have failed, tracks are inadequate, the problem of treating them at junctions and intersections is completely unsolved, and the attitude of the cyclists themselves to these admittedly unsatisfactory tracks has not been as helpful as it might have been".
Primary safety 
The state of knowledge regarding primary safety has advanced significantly through programmes such as Effective Cycling and the development of Britain's new National Standards for cycle training. In addition to technical improvements in brakes, tyres and bicycle construction generally (for example, it is now rare for a chain to snap and throw the rider when accelerating away from a stop), there are well-understood behavioural models which actively manage the risk posed by others.
Most important among these is the understanding of road position.
Safe Cycling 
Much of what is covered here will be found in the syllabus of a thorough cycling course. Cycle training has developed very considerably in the last couple of decades, and any new or returning cyclist, adult or child, is likely to benefit from formal training from an accredited instructor. At the very least it's worth riding out with an experienced "bike buddy" who can help you get started.
Road position 
Best practice puts the cyclist's wheels more or less where the nearside wheels of the motor traffic would normally go (the "secondary riding position") or, at points of particular danger such as junctions and width restrictions, in the centre of the lane (the "primary riding position" or "taking the lane").
The majority, 73% according to UK data, of car/cyclist collisions occur at junctions or "junction type" locations. Analysis of T-junction  and Roundabout collisions has indicated that failure to yield by entering motorists is a significant accident type. Other significant collision types involve turning-motorists failing to yield to oncoming cyclists and so-called "hook" or "overtake and turn" type maneuvers. Expert opinion has it that, having taken due account of the nature and speed of any following traffic, cyclists may best protect themselves from such collisions by adopting a prominent road position approaching junctions.
This has two functions: first, it places the cyclist where drivers are actively looking. Second, motorists must "overtake" so may be discouraged from simply driving past the cyclist and then turning across them. Similarly, away from junctions, a prominent position correctly communicates the space the cyclist needs and makes passing a matter of overtaking properly, rather than squeezing past. Additionally most minor injuries to cyclists, possibly up to 85%, result from simple falls. Arguably, keeping out from the curb also keeps the cyclist away from potential hazards such as drainage grates, gutters, potholes, roadside debris, loose gravel and glass etc. However, a sense of caution is required, what works in urban conditions for someone like a young adult sports-cyclist may not work for someone else who is less able or experienced. As with all road users, cyclists should try to exercise common sense and use gradual experience to build up to new traffic situations.
The advice on positioning contrasts with a lot of information historically given out in basic cycle training for children, and appears to conflict with the vehicle codes in a number of jurisdictions, which will often require a cyclist to ride as far into the gutter as possible. Many drivers also feel that a cyclist has no right to use the road, and that cyclists should be as close to the margin as possible so as not to interfere with their speedy passage. It is worth remembering that no highway code is intended to actively endanger life; the wording may be careless or possibly ignorant but should be interpreted as meaning as far toward the margin as is consistent with safety - and that might mean in the middle of the lane.
Road hazards 
General Hazards 
Never ride a cycle along the passenger side of a large vehicle, such as an HGV or bus. Exercise extreme care when you are passing vehicles of this type, particularly on the passenger side, if the driver decides to make a turn across your direction of travel you will be in a potentially fatal situation. According to the City of London cycling guide  "over half of cyclist fatalities in the central London involve left turning lorries"
Try to avoid potholes where you can, but if you have to ride through them stand up on the pedals and take your weight off the saddle. This will reduce the strain on the wheels, the frame and your body, and also mean you don't lose as much speed. The same technique applies to cobbled streets or particularly bad road conditions. Experienced cyclists learn to negotiate potholes and rough patches with bunny hops or through a procedure known as "getting light". Getting light is essentially a bunny hop that does not leave the ground, but results in the wheels' being relieved of most of the rider's weight. Toeclips or clip-less pedals make all varieties of bunny hop much easier.
In very slippery conditions (e.g. snow, ice, mud or wet leaves), avoid using the front brake and rely on the rear to slow down. A front wheel skid will invariably result in the bike falling over.
Metal drain covers are often placed in the part of the road where cyclists ride, particularly at junctions. These become slippery in wet weather especially after a dry period when rubber particles and a film of oil have built up.
A variant on this is the drainage grating with slots that run parallel to the direction of travel. These can easily grab a cycle wheel and cause a crash. Waffle plates and other alternative bicycle-safe designs use holes that will not grab a bicycle wheel; best practice indicates that cyclists should in any case ride further out than the drainage grates.
Bridges usually have expansion joints. Some leave gaps large enough to grab a bicycle wheel. Most can be crossed safely, carefully, at an angle.
Railway tracks crossing the road combine polished metal surfaces and deep channels that can trap a wheel and throw the rider off the bike. When crossed perpendicularly they usually cause only a jolt, but tracks crossing the roadway at an angle are much more apt to grab the front wheel. The standard advice is to cross tracks at a right angle, or as near to a right angle as possible. Tram lines running parallel to the line of travel of cyclists require particular alertness. Whilst a bus or lorry driver can be prosecuted for dropping a bit of slippery oil, long slippery rails are inherent to the design of a tramway.
Speed bumps 
Speed bumps used as traffic calming devices on public roads are designed according to an accepted standard and yet present some hazard to cyclists. Some of the desirable design features are a smooth transition from the road surface and a limited slope. Speed bumps on many roads and parking lots don't meet these standards, and are usually of a design which present a hazard to cyclists. One example is a bolt-on rubber speed bump with an abrupt edge that can cause a bicycle front wheel to turn sharply and eject the cyclist.
A UK spec speed table is particularly savage, constructed with flat paving brick tops and concrete slab slopes. This limits the speed at which a cyclist can approach, particularly with small wheels. Because of the sand core the paving surface is dislodged by heavy vehicles (buses, dust carts etc.) and the surface soon becomes uneven.
Slippery (Icy) Conditions 
On very slippery surfaces, even a minor lean to one side can cause the whole bike to slip, and the biker to fall over. However, it is still possible to bike in these conditions. In fact, depending on the surface properties of the road or pathway, the likelihood of slipping into an accident on a bike is arguably less than that of in a car or on foot. However, a winter rider must do things differently than a summer rider.
First, the seat of the bike should be lowered so that both the rider's feet can touch the ground at the same time. This is done so that, if the bike does slip, then the rider can support the bike with his legs. Having both feet down creates a stable structure. Note that lowering the seat will make riding more difficult, as the rider cannot fully extend his legs when pedaling. Also, the rider should not use clipless pedals nor toe clips to insure that the feet can quickly extend to the ground.
When biking in slippery conditions, it is sometimes recommended to use the rear brakes rather than the front ones. Note, however, that in non-slippery conditions, it is recommended that the front brakes are always used. The use of rear brakes in slippery conditions is for the same reason that cars have anti-lock brakes on their front wheels; since the front wheels are used for steering, then the rider/driver is unable to steer when these wheels lock up. Thus, it is recommended to only use the rear brakes when possible, in case the bike starts to slip and a course adjustment is necessary.
Lastly, studded tires are a wise investment in climates with prolonged slippery conditions. These tires add much-needed traction to the bike itself. In most locations with long winters, any reputable bike shop will sell studded tires.
As a moving vehicle brakes, the vehicle applies a forward force on the road, and the road applies an equal and opposite backward force on the wheel. When braking a bike at maximum deceleration, all the force is transferred to the front wheel, and the rear wheel is on the point of lifting. It follows from this that the front brake provides more braking force than the rear. Many riders are reluctant to use the front brake fully for fear of going over the handlebars, and some old-fashioned training encouraged use of the back brake.
Modern direct-pull cantilever brakes (e.g. Shimano's V-brake) are very effective. Riders who are unfamiliar with these brakes might easily apply more brake force than intended and lose control. Novice or returning riders should learn how to brake properly using primarily the front brake. One exception, when rear brakes should be used over front brakes, is in very slippery road conditions. In these circumstances, if the front tire locks up (because of braking), then it will not be able to steer the bike, and a frontwheel slide can result. Using the rear brake allows the rider to steer while braking. Prudent riders practice braking and turning until they have a good feel for how the bike will handle under heavy braking. Cadence braking can help decide which brake to use; use as much brake force as you can get but without locking that wheel. On a well-maintained bike and having practiced properly it is very unlikely that a rider will go over the handlebars when braking, typically half a g (5m/s^2) which is more than the coefficient of friction between the tyre and a wet road.
Brakes generate heat. On long descents, or stopping from speed, this causes rim brakes to lose efficacy - this is known as brake fade (cars get this too). If the rider sits up straight, air resistance will provide much of the braking force, and the cycle will reach a limiting speed of under 25mph except on the steepest of roads. The rear brake can also be used to gently slow a descent. The front brake should be used in combination with the rear so as to avoid overheating either one. Disc brakes are less prone to fade, but it does happen.
Water degrades braking efficiency. Rim brakes in particular will not work until the rim is dry, potentially losing valuable seconds. Always brake early in wet weather, and if the roads have recently been dry watch out for oil lifted from the road surface. Steel rims become nearly frictionless when wet. When steel rims were the norm it was possible to buy leather brake blocks which worked in the wet; these are now hard to find. In practice the best thing to do with a steel rim may be to replace it with an aluminum one.
Cycle paths 
Cycle paths have a checkered history. Standards of design, construction and maintenance vary widely.
Statistically, cycle paths have an indifferent safety record. This is largely a result of loss of priority and conflicts at junctions. In general, a cycle path reduces risk between junctions, but greatly increases danger at junctions. The balance of danger will depend on the frequency of junctions and other crossings. Width is also an issue: the minimum recommended width for a cycle path is around 2m, but some are very much narrower. Maintenance can also be patchy; glass and potholes are common. Shared-use facilities, shared with pedestrians, are generally considered to be least satisfactory.
On-road cycle lanes are also a mixed blessing. Some are well designed, and the advanced stop line (a section of road which allows cyclists to clear junctions ahead of motor traffic) is generally appreciated by cyclists. But some cycle lanes are too narrow, disappear at the point of greatest danger, take the rider out of the line of sight at junctions, are ill-maintained or littered with debris. For the most part, road cyclists agree that the main carriageway is preferable both for visibility and because the passage of traffic sweeps away any debris.
See also 
- How to reduce the odds of a collision with other vehicle operators
- "EXTENT AND SEVERITY OF CYCLE ACCIDENT CASUALTIES". Scottish Executive. 2005-08-09. http://www.scotland.gov.uk/Publications/2005/07/1993846/38477.
- Davis R, Death on the Streets: Cars and the mythology of road safety
- Davis R "Death on the Streets:Cars and the Mythology of Road Safety." Leading Edge 1993
- "The cost of bad design". The Commission for Architecture and the Built Environment (CABE). 2006. http://www.cabe.org.uk/AssetLibrary/8125.pdf.
- H.A. Tripp (1942). Town Planning and Road Traffic. E. Arnold.
- Colin Buchanan (1958). Mixed Blessing. L Hill.
- "Irish Junction Design Practice". Galway Cycling Campaign. http://www.eirbyte.com/gcc/info/irish_junctions.html. Retrieved 2006-05-16.
- "Multilane Roundabouts". Galway Cycling Campaign. http://www.eirbyte.com/gcc/info/roundabouts.html. Retrieved 2006-05-16.
- [http://www.cycle-helmets.com/bicycle_crashes.html "Bicycle Crashes and Injuries in Western Australia"]. cycle-helmets.com. http://www.cycle-helmets.com/bicycle_crashes.html. Retrieved 2006-08-27.