<P> While in general, wider lanes are associated with a reduction in crashes, in urban settings both narrow (less than 2.8 m) and wide (over 3.1 ~ 3.2 m) lanes increase crash risks . Wider lanes (over 3.3 ~ 3.4 m) are associated with 33% higher impact speeds, as well as higher crash rates . Carrying capacity is also maximal at a width of 3 to 3.1 metres (9.8 to 10.2 ft), both for motor traffic and for bicycles . Pedestrian volume declines as lanes widen, and intersections with narrower lanes provide the highest capacity for bicycles . As lane width decreases, traffic speed diminishes . </P> <P> Advocates for safety of people walking and people on bikes, and many new urbanists disagree with traditional thinking in traffic engineering, saying that safety and capacity are not adversely impacted by reducing lanes widths to as little as 10 feet (3.0 m). Moreover, wider travel lanes also increase exposure and crossing distance for pedestrians at intersections and midblock crossings . </P> <P> The widths of vehicle lanes typically vary from 9 to 15 feet (2.7 to 4.6 m). Lane widths are commonly narrower on low volume roads and wider on higher volume roads . The lane width depends on the assumed maximum vehicle width with an additional space to allow for lateral motion of the vehicle . </P> <P> The maximum truck width had been 96 inches (2.438 m) in the Code of Federal Regulations of 1956 which matches with the width of eight - foot for shipping containers . This had been increased to 102 inches (2.591 m) in 1976 which explicitly states to be read as the slightly larger metric 2.6 metres (102.36 in) width respecting international harmonization . The same applies to standards in Europe which had increased the allowable size of road vehicles with a current maximum of 2.55 metres (100.39 in) for most trucks and allowing 2.6 metres (102.36 in) for refrigerator trucks . The minimum extra space had been 0.20 metres (7.87 in) and it is currently assumed to be at least 0.25 metres (9.84 in) on each side . For roads with a lower amount of traffic it is allowed to build the second or third lane in the same direction to an assumed lower width for cars like 1.75 metres (68.90 in), however this is not recommended as a design principle for new roads as changes in the amount of traffic could make for unnecessarily increased risks in the future . </P>

How wide is a standard lane of traffic