Synthesis of Safety for Traffic Operations - Transports Canada

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Synthesis of Safety for Traffic Operations March 2003 The Tople analysis possesses many potentially serious flaws. Most importantly, the sites were selected for treatment as part of a safety program. This means that the crash record was likely abnormally high, and there is a great potential for regression to the mean artefacts. This shortcoming is likely offset somewhat by a failure to account for changes in exposure. Traffic volumes were not controlled for, but typically volumes tend to increase which would lead to a higher “after” count of crashes. In the end, the South Dakota results are based on a limited number of sites and weak analyses. Ministry of Transportation for Ontario (1998) The Ministry of Transportation for Ontario (MTO, 1998) undertook a comprehensive study of the crash data to determine the safety performance of their facilities, including intersections. In the conduct of the study, SPFs, disaggregated by severity, were developed for signalized intersections owned by the province of Ontario. The form of the SPF is shown in Equation 3.2, the estimates of the parameters are shown in Table 3.7. N = a AADT b [3.2] where: N = annual number of crashes AADT = Average annual daily traffic of the main road a, b = parameters are shown in Table 3.10 Intersection Type Signalized, 4 approaches Signalized, 3 approaches TABLE 3.7: SPFs for Ontario Signalized Intersections Collision Type a b AADT Range Fatal Injury PDO Fatal Injury PDO 0.0002283 0.0103469 0.0169214 0.0000853 0.0038654 0.0063216 0.54866 1,090 to 34,280 0.54925 4,600 to 28,460 A SPF for unsignalized intersections in Ontario was not developed by the MTO. This limits the usefulness of the SPF for signalized intersections. Nonetheless, the SPF is helpful as a measure of safety. Sayed and Rodriguez (1999) Sayed and Rodriguez (1999) developed SPFs for unsignalized intersections in British Columbia using crash and traffic volume data from urban intersections in the Greater Page 19
Intersection Control Vancouver Regional District, and Vancouver Island. The dataset included 186 intersections with three-legs and 233 intersections with four legs. Three years of data were used in the model development, sites were selected on the basis of available data. Only one-way (at T-intersections) and two-way (at cross intersections) stop controlled intersections were included in the analysis. Crashes that were within 30 metres of the intersection, or were coded as “intersection-related” were defined as intersection crashes. The range of data used in the analysis is shown in Table 3.8. TABLE 3.8: Data Ranges Used in Developing SPFs for Urban, Unsignalized Intersections Variable Statistic Minimum Maximum Mean Major Road ADT 500 47,800 13,343 Minor Road ADT 100 11,000 1,735 Crashes/year 0.3 11 1.72 SPFs were developed using generalized linear modeling assuming a negative binomial distribution. The model form is shown in Equation 3.3, the parameters are as shown in Table 3.9. N = a(AADT major /1000) b1 (AADT minor /1000) b2 [3.3] where: N = Crashes per 3 years AADT major = Average annual daily traffic of the major road AADT minor = Average annual daily traffic of the minor road a, b1, b2 = constants as shown in Table 3.7 TABLE 3.9: SPFs for Urban, Unsignalized Intersections in BC No. Approaches a b 1 b 2 3 0.9333 0.4531 0.5806 4 1.5406 0.4489 0.6475 Vogt (1999) Vogt (1999) developed crash models for rural signalized and stop-controlled intersections using combined data from Michigan and California. Eighty-four stop-controlled intersections with three approaches, 72 stop-controlled intersections with four approaches, and 49 signalized intersections with four approaches were included in the analysis. The stop-controlled intersections had four lanes on the main road, and two Page 20
Page 1 and 2: Transport Canada Transports Canada
Page 4: Synthesis Of Safety For Traffic Ope
Page 8 and 9: DISCLAIMER The material presented h
Page 10 and 11: EXECUTIVE SUMMARY Traffic operation
Page 12 and 13: Synthesis of Safety for Traffic Ope
Page 16 and 17: TABLE OF CONTENTS DISCLAIMER REJET
Page 20 and 21: LIST OF TABLES TABLE 3.1: Crash Rat
Page 24: Chapter 1: Chapter 1: Introductio I
Page 27 and 28: Introduction Before proceeding, a f
Page 29 and 30: Introduction Literature regarding t
Page 31 and 32: Introduction The current science of
Page 33 and 34: Introduction adequate size control
Page 35 and 36: Introduction In concluding this sec
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Page 45 and 46: Intersection Control TABLE 3.3: Cra
Page 47: Intersection Control TABLE 3.5: CMF
Page 51 and 52: Intersection Control V m = the sum
Page 53 and 54: Intersection Control where: X1 = 0
Page 55 and 56: Intersection Control Region of Durh
Page 57 and 58: Intersection Control TABLE 3.17: CM
Page 59 and 60: Intersection Control The predictor
Page 63 and 64: Intersection Control program includ
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Page 67 and 68: Intersection Control TABLE 3.29: St
Page 69 and 70: Intersection Control TABLE 3.32: Ni
Page 73 and 74: Intersection Control It is noted th
Page 75 and 76: Intersection Control Sayed et al (1
Page 77 and 78: Intersection Control Signal Clearan
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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Synthesis of Safety for Traffic Ope
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Chapter 5: Chapter 5: Pavement Pave
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Pavement Markings The study methodo
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Pavement Markings Hall (1987) Hall
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Pavement Markings TABLE 5.8: Safety
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Pavement Markings THIS PAGE IS INTE
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Chapter 7: Chapter 7: Bicycle Bicyc
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Bicycle Safety TABLE 7.1: Safety Im
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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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Synthesis of Safety for Traffic Operations - Transports Canada

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