DOES REDUCING TRAFFIC SPEED USING SPEED CAMERAS REDUCE THE NUMBER OF COLLISIONS?
7.13 Acknowledgements, references and supplementary information for report
The author would like to thank TVSRP (Thames Valley Safer Roads Partnership) for supplying the database of collisions at camera sites along with all supplementary information that was requested and received.
The author would also like to thank the engineers, officers and proof readers who assisted in the production of this report.
1. TRL 58 1994: Finch DJ, Kompfner P, Lockwood CR and Maycock G (1994). Speed, speed limits and accidents. Transport Research Laboratory TRL Project Report 58. Crowthorne.
2. TRL 421 2000: Taylor M, Lynam D and Baruya A (2000). The effects of drivers’ speed on the frequency of road accidents. Transport Research Laboratory TRL Report 421, Crowthorne. Download TRL421.pdf.
3. Police investigations find that 5.5% of collisions in Thames Valley involve a vehicle exceeding a speed limit, speeding Table 1.4. Nationally, over the most recent 6 years 2005-2010, the figure is 5.1% on average, speeding Table 1.1.
4. Official reports on speed cameras have:
4a ignored the effect - such as the DfTs 2 year pilot evaluation
4b used complicated formulae to predict collision rates - such as the DfTs 4 year evaluation
4c used sites not eligible for cameras as comparison sites - such as West London Speed Camera Demonstration Project
4d used theoretical models - such as The Effectiveness of Speed Cameras - RAC Foundation
5. TVSRP installed the vast majority of mobile camera sites but stated by email (Monday, 21/June/2010 4:34 PM) "… each site will have not received a speed survey before installation and then after to assess the effect to speeds at the site since installation. It would not be possible to analyse before and after speeds at sites simply because we do not hold it".
FOI (Freedom Of Information) requests were sent to all local authorites in Thames Valley, the Thames Valley Police and DfT (Department for Transport) but all stated they have no data on changes in speed at any mobile sites in Thames Valley.
6. The national safety camera programme Four-year evaluation report December 2005: UCL, PA Consulting, Adrian Gains, Michael Nordstrom, Benjamin Heydecker, John Shrewsbury, Linda Mountain, Mike Maher. Download 4-year evaluation.
Change in average speed at mobile camera sites nationally in The Four-year evaluation is -1.3 mph (p28, table 2.4) for all roads and examination of the speed surveys found (p30) "...we conclude that the reductions were not just ‘ one-off’ but were sustained over time. In fact, for mobile sites, the one-off reductions were not only sustained but actually strengthened further as sites matured."
7. Average speeds at fixed camera sites in Thames Valley from Police website on Speeds_at_Fixed_cameras_Police.xls. The only data available was from 39 fixed camera sites in Buckinghamshire. FOI (Freedom Of Information) requests were sent to TVSRP and all local authorites in Thames Valley but all stated they have no data on changes in speed at any other fixed camera sites in Thames Valley.
8. Four-year evaluation (p91) Table A1 Site selection guidelines. For fixed sites the site length can be "Between 400-1500 metres" and, for mobile sites, the site length can be "Between 400 and 3000 metres".
9. Four-year evaluation report (p156) "...part of the reduction in collisions attributable to the cameras may be due to diversion of traffic away from routes with cameras."
10. Criteria for proposed speed camera sites after 2001 can be found in the 4-year evaluation and states (p91) "9. No other engineering solutions are appropriate" and "There has been a site survey by a qualified road safety engineer and there are no obvious viable measures to improve road safety along this stretch of road"
The database of collisions on which this report is based was supplied by TVSRP (Thames Valley Safer Roads Partnership).
During the first quarter of 2009, TVSRP undertook a full check and correction procedure on their collision records to produce a verified database of collisions at all camera sites. This report is based on the new verified database supplied by TVSRP containing the number and severity of collisions at every camera site in Thames Valley within each calendar month from Apr 1990 to Mar 2009 inclusive (a 19-year period consisting of 228 individual months of data for every site). Only data before 01 Jan 2009 is used in this report because it was considered that the very latest police collision reports may not have been submitted or included for the final 3 months.
The complete database contains a total of 517 camera sites. Of these 235 are fixed camera sites but 23 of these have been decommissioned. This report includes all 212 active fixed camera sites.
The database contains a total of 261 mobile camera sites but 89 of these have been decommissioned. A further 67 of the active sites were installed after the start of 2007 and therefore had insufficient data for this report having been operating for under 2 years by the start of 2009. This report includes all 105 active mobile camera sites operating for over 2 years.
Excel spreadsheet with camera site information: 5per1mph.xls
6 graphs displayed in 3 pairs. There are a pair of graphs each for all camera sites, fixed sites and mobile sites. The 1st of each pair shows collisions in each month for the 2 years before and 2 years after installation. The 2nd of each pair shows the percentage of annual Thames Valley collisions in each month for the 2 years before and 2 years after installation.