Bigdeli et al. BMC Public Health 2010, 10:406 http://www.biomedcentral.com/1471-2458/10/406 Page 4 of 7 Table 2 Pre-hospital time intervals of road traffic injury stratified by crash location in the Urmia from 20 March 2005 to 20 March 2007 Time intervals (minute)* Activation interval Response interval On-scene interval Transport interval Total pre-hospital Mean (SD) 1.4 (0.6) 5.0 (3.1) 6.1(3.7) 6.3 (3.6) 29.2 (9.1) City Median (0.25%-0.75%) 1 (1-2) 4 (3-7) 5 (4-7) 5 (4-8) 28 (22-34) Mean (SD) 1.4(0.6) 10.6 (7.0) 9.2 (6.7) 17.1(10.9) 49.9 (19.4) Interurban roads Median (0.25%-0.75%) 1 (1-2) 9 (6-13) 7 (5-11.3) 14 (9-23) 45 (35-62) *Despite of activation interval, all P-values were < 0.001 20 minutes of departure from the crash scene. Close to half of the cases on interurban roads reached the hospi- tal more than 45 minutes after departure (P < 0.001). As Table 4 shows, seven out of ten of the injuries occurred between 8.00 am and 8.00 pm. There was an association between time of injury occurrence and crash site (P < 0.001); of which close to half of the injuries on interurban roads occurred between 14:01- 20:00, which at the same time this is different from the injury occurrence in the city area. There was an asso- ciation between the victims’ crash site and the days of the week (P = 0.02). Table 3 Proportion of the different time intervals of road traffic injury stratified by crash location in the Urmia from 20 March 2005 to 20 March 2007 City Time intervals (minute) N = 1246 Interurban roads N = 781 Total N = 2027 Activation interval ≤ 2 > 2 Response interval < 8 8-15 > 15 % % 98.1 99.2 1.9 0.8 Chi-square= 0.9; P = 0.29 89.2 45.7 9.4 34.3 1.4 20.0 Chi-square= 301.3; P < 0.001 On-scene interval < 5 51.2 37.2 5 -10 39.5 34.3 > 10 9.3 28.5 Chi-square= 82.9; P < 0.001 Transportation interval < 10 88.8 34.0 10-20 10.7 37.5 > 20 0.5 28.5 Chi-square= 450; P < 0.001 Total interval < 30 30-45 > 45 79.5 25.1 17.2 30.6 3.3 44.3 Chi-square= 454; P < 0.001 % 98.5 1.5 72.5 18.9 8.6 45.8 37.5 16.7 67.7 21.0 11.3 58.5 22.4 19.1 The effect of the date and season of injury on the mean time intervals (response time, transport time and total time interval) of the ambulance dispatches was also explored in this analysis. As Table 5 shows, there was an association between the mean of the above time intervals during weekdays at crash location (P < 0.05). However, none of the time intervals varied significantly between city and interurban roads areas, when the time intervals were stratified according to season (P < 0.05). Discussion This study estimated the various time intervals for ambulance services and the differences between them Table 4 Proportion of the time of RTIs occurrence at city and interurban roads in the Urmia from 20 March 2005 to 20 March 2007 Time, date and season of injury Time of injury 08:01-14:00 14:01-20:00 20:01-02:00 02:01-08:00 Date of injury Sunday Monday Tuesday Wednesday Thursday Friday Saturday Season of injury Spring Summer Autumn Winter City N = 1246 Interurban roads N = 781 Total N= 2027 % % % 33.0 29.8 31.7 35.3 48.2 40.3 26.1 16.7 22.5 5.6 5.3 5.5 Chi-square= 25.1; P < 0.001 13.9 13.6 14.8 13.3 16.5 15.1 12.8 33.5 28.8 20.9 16.8 14.2 10.1 14.8 14.0 12.1 21.8 13.0 Chi-square= 14.8; P = 0.02 34.8 26.1 24.1 15.0 Chi-square= 3.0; P = 0.3 14.0 12.2 14.8 13.6 14.8 17.7 12.9 34.0 27.8 22.1 16.1