Assessing the Risk to London Cyclists from Mayoral Policy



Assessing the Risk to London Cyclists from Mayoral Policy

Authors

B Lewis, Transport for London, UK

Description

Declaring 2010 the year of the bicycle, the Mayor of London has set an ambitious target for cycling levels in London with a mode share of 5% of all trips by 2025, effectively a quadrupling of the level of cycling activity in London.

Abstract

Declaring 2010 the year of the bicycle, the Mayor of London has set an ambitious target for cycling levels in London with a mode share of 5% of all trips by 2025, effectively a quadrupling of the level of cycling activity in London. Transport for London recently reported a 91% rise in cycling on its road network since 2001. By investigating the relationship between vehicle flow and cycle accidents this paper seeks to determine a methodology for assessing the risk to cyclists using modern methods of statistical analysis.
13% of all reported road traffic collisions in Greater London in 2007 resulted in injury to pedal cyclists compared to 22% for pedestrians. In terms of modal share, pedal cyclists account for less than 2% of all trips in London compared to 20% for pedestrians.
As pedal cycle activity in London is expected to quadruple by 2025 from 2001 levels there is a growing awareness among transport professionals that current methods of policy appraisal and evaluation are insufficient in being able to reflect the resulting change in modal share. Planners need practical tools to consider the impact of development on safety targets, a key requirement for the promotion of cycling.
Current advice by the Department for Transport is to use an exponent function to estimate accident numbers resulting from an increase in average flow. This paper reviews DfT methodology using London data and seeks to provide policy makers with a more robust methodology using negative binomial regression of site-specific road characteristics: mode share, speed, delay, population density, length of link and number of lanes were tested for significance and a new accident exponent function was found.
The results of this study indicate that a negative binomial regression model that uses publicly available data provides a rigorous methodology that can be used to assess the risk that pedal cyclists face on the road network on a link by link basis.

It was found that the exposure rate for central and inner London is up to five times larger using the bespoke model output rather than aggregated statistics. The model predicts that a quadrupling of cycle activity from 2001 levels without the inclusion of any additional complementary safety measures would result in a 50% increase in accidents in central London and a 30% increase in inner London.

Notably, the year variable was included as a proxy for the memory effect within the zone but was found to be highly insignificant. That is, the null hypothesis that drivers within the zone have become more used to sharing the road space with pedal cycles over time and adjusted their driving behaviour accordingly was rejected. However, for policy makers, it is encouraging that the model predicts increasing cycling levels in inner London should have a larger effect on reducing relative accident exposure than within central London.

It is recommended that the number of accidents predicted by the new model is used to assess the success of Mayoral policy. Cycling superhighways and cycle hire schemes may achieve the Mayor?s aim of increasing mode share, but the true success will be measured in terms of public safety.

Publisher

Association for European Transport