Primary position

A dull sounding US report, but with some quite interesting findings (following on from Walker's: "Drivers overtaking bicyclists: Objective data on the effects of riding position, helmet use, vehicle type and apparent gender" 2006).

Operational and Safety Impacts of Restriping Inside Lanes of Urban Multilane Curbed Roadways to 11 Feet or Less to Create Wider Outside Curb Lanes for Bicyclists
Septmeber 2011

The relationship between a motor vehicle’s distance from other motor vehicles and the lateral positioning of bicyclists from the curb is depicted in Figure 6. Intuitively, one would expect that the closer you ride to the curb, the more lateral separation you have. On the contrary, the results presented in Table 4 and Figure 6 show that riding closer to the curb results in a smaller separation. Field observations revealed that when bicyclists ride closer to the curb, some motor vehicles, especially compact cars attempt to fit in the lane without laterally shifting to the adjacent lane, hence causing lesser distance. On the other hand, the results show that riding too far from the curb also results in a shorter distance. It seems that there is a spot between 3 and 4 ft from the curb that results in the greatest lateral separation between motor vehicles and bicyclists. It should be noted however, that higher standard deviations were observed. This was mainly caused by the fact that some drivers choose to stay within the outside through lane while others laterally shift to the inside lane.