Lane splitting
Lane splitting is riding a bicycle or motorcycle between lanes or rows of stopped or slow traffic moving in the same direction. It is sometimes called whitelining, or stripe-riding. This allows riders to save time, bypassing traffic congestion, and may also be safer than stopping behind stationary vehicles.
Filtering or filtering forward is to be contrasted with lane splitting. Lane filtering refers to motorcycles moving through traffic that is stopped, such as at a red traffic light.
In the developing world
In population-dense and traffic-congested urban areas, particularly in the developing world, the space between larger vehicles is filled with a wide variety of different kinds of two-wheeled vehicles, as well as pedestrians, and many other human or animal powered conveyances. In places such as Bangkok, Thailand and in Indonesia, the ability of motorcycles to take advantage of the space between cars has led to the growth of a motorcycle taxi industry. In Indonesia, the motorcycle is the most common type of vehicle.Unlike typical developed nations that have only a handful of vehicle types on their roads, many types of transport will share the same roads as cars, buses and trucks; this diversity is extreme in Delhi, India, where more than 40 modes of transportation regularly use the roads. In contrast, New York City, for example, has perhaps five modes, and in parts of America a vast majority of traffic is made up of two types of vehicles on the road: cars and trucks.
It has been suggested that highly diverse and adaptive modes of road use are capable of moving very large numbers of people in a given space compared with cars and trucks remaining within the bounds of marked lanes. On roads where modes of transportation are mingled this can cause a reduced efficiency for all modes.
Safety
Filtering forward, in stopped or extremely slow traffic, requires very slow speed and awareness that in a door zone, vehicle doors may unexpectedly open. Also, unexpected vehicle movements such as lane changes may occur with little warning. Buses and tractor-trailers require extreme care, as the cyclist may be nearly invisible to the drivers who may not expect someone to be filtering forward. To avoid a hook collision with a turning vehicle at an intersection after filtering forward to the intersection, cyclists are taught to either take a position directly in front of the stopped lead vehicle, or stay behind the lead vehicle. Cyclists should not stop directly at the passenger side of the lead vehicle, that being a blind spot.Research
Little safety research in the United States has directly examined the question of lane splitting. Both the US 1981 Hurt Report and the European 2004 MAIDS report studied the causes of motorcycle accidents yet reached no conclusion as to whether lane splitting contributed to or prevented accidents.Lane splitting is never mentioned anywhere in the Hurt Report, and all of the data was collected in California, so no comparison was made between of lane splitting vs. non-lane splitting. The Hurt Report ends with a list of 55 specific findings, such as "Fuel system leaks and spills are present in 62% of the motorcycle accidents in the post-crash phase. This represents an undue hazard for fire." None of these findings mentions lane splitting, or rear-end collisions. The legislative and law enforcement advice that follows this list does not mention lane splitting or suggest laws be changed with regard to lane splitting.
In Europe, the MAIDS Report was conducted using Organisation for Economic Co-operation and Development standards in 1999–2000 and collected data on over 900 motorcycle accidents in five countries, along with non-accident exposure data to measure the contribution of different factors to accidents, in the same way as the Hurt Report. Four of the five countries where data was collected allow lane splitting, while one does not, yet none of the conclusions contained in the MAIDS Final Report note any difference in rear-end accidents or accidents during lane splitting. It is notable that the pre-crash motion of the motorcycle or scooter was lane-splitting in only 0.4% of cases, in contrast to the more common accident situations such as "Moving in a straight line, constant speed" 49.1% and "Negotiating a bend, constant speed" 12.1%. The motorcyclist was stopped in traffic prior to 2.8% of the accidents.
Preliminary results from a study in the United Kingdom, conducted by the University of Nottingham for the Department for Transport, show that filtering is responsible for around 5% of motorcycle Killed or Seriously Injured accidents. It also found that in these KSI cases the motorist is twice as likely to be at fault as the motorcyclist due to motorists "failing to take into account possible motorcycle riding strategies in heavy traffic".
A very different form of research, where the capacity benefits are examined as well, 1500 powered two-wheelers were video tracked to calibrate an agent based model of movement between and along lanes, also included a Bayesian model calibrated to determine the choices made to move between lanes. This model provides a basis for measuring the risk levels of such choices, and late applications allowed the determination of the capacity gains from such movement once filtered to the front of the queue and in continuing non-intersection movements along stretches of road
Belgian policy research company Transport & Mobility Leuven published a study in September 2011 investigating the effects that increased motorcycle usage would have on traffic flow and emissions and found that a 10% modal shift would result in a 40% reduction in commute time and a 6% reduction in total emissions. This calculation assumed that all motorcycles moved between lanes and the space used by them, called a passenger car equivalent, would be reduced to zero when traffic came to a complete standstill. It also assumed that motorcycles would overtake cars without hindering them during heavy congestion, and PCE would be between less than 0.5, approaching zero as traffic density increased.
Debate over safety and benefits
Proponents state that the practice relieves congestion by removing commuters from cars and gets them to use the unused roadway space between the cars, and that lane splitting also improves fuel efficiency and motorcyclists' comfort in extreme weather. In the US, transportation engineers have suggested that motorcycles are too few, and will remain too few, to justify any special accommodation or legislative consideration, such as lane splitting. Unless it becomes likely that a very large number of Americans will switch to motorcycles, they will offer no measurable congestion relief, even with lane splitting. Rather, laws and infrastructure should merely incorporate motorcycles into normal traffic with minimal disruption and risk to riders.Potentially, lane splitting can lead to road rage on the part of drivers, who feel frustrated that the motorcyclists are able to filter through the traffic jam. However, the Hurt Report indicates that, "Deliberate hostile action by a motorist against a motorcycle rider is a rare accident cause." Lane splitting is not recommended for beginning motorcyclists, and riders who do not practice it in their home area are strongly cautioned that it can be risky if they attempt it when traveling to a jurisdiction where it is allowed. Similarly, for drivers new to places where it is done, it can be startling and scary.
Responsibility and liability issues
Another consideration is that lane splitting in the United States, even where legal, can possibly leave the rider legally responsible. According to J.L. Matthews in How to Win Your Personal Injury Claim:When the 2005 bill to legalize lane splitting in Washington State was defeated, a Washington State Patrol spokesman testified in opposition, saying that, "it would be difficult to set and enforce standards for appropriate speeds and conditions for lane splitting." He also said that officials with the California Highway Patrol told him that they wished they had never begun allowing the practice. the California Highway Patrol has lane splitting tips on their website. Similar guidelines were posted by the California Department of Motor Vehicles, but those guidelines were subsequently removed.
Safety aspects
California's DMV handbook for motorcycles advises caution regarding lane splitting: "Vehicles and motorcycles each need a full lane to operate safely and riding between rows of stopped or moving vehicles in the same lane can leave you vulnerable. A vehicle could turn suddenly or change lanes, a door could open, or a hand could come out the window." The Oxford Systematics report commissioned by VicRoads, the traffic regulating authority in Victoria, Australia, found that for motorcycles filtering through stationary traffic "o examples have yet been located where such filtering has been the cause of an incident."In the United Kingdom, Motorcycle Roadcraft, the police riding manual, is explicit about the advantages of filtering but also states that the "...advantages of filtering along or between stopped or slow moving traffic have to be weighed against the disadvantages of increased vulnerability while filtering".
After discussing the pros and cons at great length, motorcycle safety guru David L. Hough ultimately argues that a rider, given the choice to legally lane split, is probably safer doing so, than to remain stationary in a traffic jam. However, Hough has not gone on record as favoring changing the law in jurisdictions where it is not permitted, in contrast to his public education and legislative efforts in favor of rider training courses and helmet use. A literature review of lane-sharing by the Oregon Department of Transportation notes "a potential safety benefit is increased visibility for the motorcyclist. Splitting lanes allows the motorcyclist to see what the traffic is doing ahead and be able to proactively maneuver." However, the review was limited and "Benefits were often cited in motorcyclist advocacy publications and enthusiast articles."