Table 1

Monthly median number of collisions and people sustaining road traffic injuries† in the pre and post-intervention periods and RR (for the post-intervention period compared with the pre-intervention period) and prevented numbers by 2 years and 5 months after the installation of speed cameras on the arterial roads, and 4 years and 9 months on the beltway

Monthly median pre-intervention (IQR)Monthly median post-intervention (IQR)RR (95% CI)Number prevented
Enforced stretches of arterial roads
 Collisions3 (3)3 (2)0.98 (0.75 to 1.27)2
 People injured5 (4)4 (2)1.37 (0.79 to 2.38)−38
Non-enforced stretches of arterial roads
 Collisions188 (32)181 (39)0.99 (0.93 to 1.05)73
 People injured262 (47)252 (50)1.00 (0.91 to 1.10)−6
Beltway
 Collisions48 (8)38 (9)0.70 (0.62 to 0.80)*913
 People injured79 (17)62 (18)0.74 (0.64 to 0.86)*1219

  • Pre-intervention periods: arterial roads: 1 January 2002–31 July 2005; beltway: 1 January 2001–31 March 2003.

  • Post-intervention periods: arterial roads: 1 August 2005–31 December 2007; beltway: 1 April 2003–31 December 2007.

  • ↵* p<0.05.

  • ↵† Includes fatal and non-fatal injuries.