Synthesis of Safety for Traffic Operations - Transports Canada

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Synthesis of Safety for Traffic Operations March 2003 models predict the annual number of crashes on an arterial approach (both directions included). Of the many variables that were found to influence crash occurrence, the type of signal control was included. Adaptive signal control was found to be safer than pretimed signal control, reducing crashes by 13% (CMF of 0.87). Night-time Flash Polanis (2002) Polanis (2002) reported on the removal of red/amber night-time flashing operation from 19 intersections in Winston-Salem, North Carolina. Site selection information is sketchy; the intersections are “not necessarily… high-crash locations”, but are described as locations where the crash pattern indicated a safety benefit from night-time flash removal. Target crashes are right-angle crashes that occur during the night-time flashing operation. The results of the study are shown in Table 3.56. Sixteen of the 19 intersections exhibited a statistically significant reduction in target crashes at the 95% level of confidence. Polanis aggregates the results for all intersections, which yields CMFs of 0.22 for target crashes, and 0.67 for all right-angle crashes. There is no reason to believe that removal of night-time flashing operation would have any measurable effect on right-angle crashes at other times of the day. Hence, rather than measuring the safety impacts on total right-angle crashes, it is more informative to use the non-target crashes (total right-angle crashes minus target crashes) as a control group. If this is the case the aggregated data produces the statistics shown in Table 3.57. These data indicate that the target crashes were reduced by 78%. However, the nontarget crashes were also reduced, by 19%. Since the night-time flashing operation should have had no effect on the non-target crashes, a 19% reduction in target crashes could reasonably be expected without removal of night-time flash. Taking into account this background crash reduction leads to a CMF for removal of night-time flashing operation of 0.27, or a 73% reduction in right-angle crashes during the flashing operation. It bears mentioning that the above study did not account for exposure. This is an important consideration because, although traffic volumes are likely increasing and omission from the analysis leads to under estimation of the safety benefits, the growth of traffic during night-time flashing operation is likely significantly less than during the remainder of the day. If this is indeed the case, then not accounting for exposure leads to an over estimation of the safety benefits of night-time flash removal. Page 59
Intersection Control TABLE 3.56: Safety Impacts of Night-time Flashing Operation Site Before After )Target )Total Months Target Total Months Target Total (crash/month) (crash/month) M:S LU ST 1 50 15 79 45 8 29 -41 -59 2:1 D F 2 33 5 18 48 0 10 -100 -62 2:1 R S 3 43 8 39 41 5 21 -34 -44 2:1 R F 4 48 8 26 48 3 26 -62 0 Na R F 5 45 12 23 45 2 25 -83 9 2:1 C A 6 48 12 23 48 1 8 -92 -65 1:1 D F 7 58 12 31 80 1 28 -94 -34 5:1 R S 8 46 6 17 43 4 14 -29 -12 2:1 R S 9 82 9 80 78 1 49 -88 -36 2:1 C A 10 22 4 10 22 0 4 -100 -60 4:1 D F 11 48 8 26 48 1 14 -88 -46 1:1 R A 12 48 7 32 48 2 17 -71 -47 3:1 C F 13 49 9 35 47 0 23 -100 -32 3:1 C A 14 46 4 23 46 2 18 -50 -22 1:1 R A 15 51 11 44 49 1 26 -90 -38 2:1 C A 16 46 4 13 45 1 16 -74 26 1:1 R A 17 45 8 25 45 2 32 -75 28 2:1 C A 18 44 5 11 44 1 12 -80 9 4:1 D F 19 36 9 57 36 0 41 -100 -28 3:1 D F • Targeted Crashes—Targeted Crashes are those crashes expected to be addressed by a particular intervention. In this instance, rightangle crashes that occurred during the hours the signal was in red/yellow flashing operation. • % targeted and % total—These refer to the percentage change in targeted and total crashes in the before and after periods (measured in crashes/month). • M:S ratio—This is the ratio of main-street to side-street traffic volumes at each intersection. • LU—This is the Land Use around the intersection: D = Downtown, R = Residential and C = Commercial. • ST—This is Signal Type: F = Fixed time, S = Semi-actuated and A = Actuated. TABLE 3.57: Safety Effects of Night-time Flashing Operation Using a Control Group Months Target Non-target Crashes Crashes Before 888 156 456 0.18/month 0.51/month After 906 35 378 0.04/month 0.42/month Page 60
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Transport Canada Transports Canada
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Synthesis Of Safety For Traffic Ope
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DISCLAIMER The material presented h
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EXECUTIVE SUMMARY Traffic operation
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Synthesis of Safety for Traffic Ope
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TABLE OF CONTENTS DISCLAIMER REJET
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LIST OF TABLES TABLE 3.1: Crash Rat
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Chapter 1: Chapter 1: Introductio I
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Introduction Before proceeding, a f
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Introduction Literature regarding t
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Introduction The current science of
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Introduction adequate size control
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Introduction In concluding this sec
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Page 42: Chapter 3: Chapter 3: Intersectio I
Page 45 and 46: Intersection Control TABLE 3.3: Cra
Page 47 and 48: Intersection Control TABLE 3.5: CMF
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Page 59 and 60: Intersection Control The predictor
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Page 75 and 76: Intersection Control Sayed et al (1
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Page 79 and 80: Intersection Control The CMFs are 0
Page 81 and 82: Intersection Control also examined
Page 83 and 84: Intersection Control Shebeeb (1995)
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Page 105 and 106: Pavement Markings The study methodo
Page 107 and 108: Pavement Markings Hall (1987) Hall
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Chapter 9: Chapter 9: Turn Lanes Tu
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Turn Lanes TABLE 9.2: Safety Impact
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Turn Lanes Vogt determined that a l
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Turn Lanes 1998 one of their high c
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Turn Lanes Section TABLE 9.10: Safe
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Turn Lanes A T = ADT 0.91 L 0.852 e
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Turn Lanes CMF = 1 - 0.7 P lt/d 0.0
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Turn Lanes occurred within 250 feet
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TABLE 10.3: Speed Changes Resulting
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Sites Where Applied 1 URBAN Island
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Forbes and Gill (2000) undertook a
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Ideally, three years of before and
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Kermit and Hein (1962) looked into
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The effects of the transverse pavem
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Chapter 11: Chapter 11: Other Other
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Other Safety Issues collisions per
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Other Safety Issues THIS PAGE IS IN
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References References
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References Bloch SA (1998) “Compa
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References Hamilton Associates (199
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References Lee JT, Maleck TL, and T
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References Polanis SF (1998) “Do
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References Vancouver, City of (1999
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References THIS PAGE IS INTENTIONAL
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Appendix B: Critical R Appendix B:
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Critical Reviews Worksheet for Eval
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Critical Reviews 2. Are the expecte
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Appendix D: Appendix D: How to Use
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How to Use Safety Performance Funct
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How to Use Safety Performance Funct
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