Available online at www.sciencedirect.com
ScienceDirect Transportation Research Procedia 20 (2017) 613 – 617
12th International Conference "Organization and Traffic Safety Management in Large Cities", SPbOTSIC-2016, 28-30 September 2016, St. Petersburg, Russia
Accident Rates at Signalized Intersections Eugene Shesterov 1а*, Alexander Mikhailov 2b 1
Saint Petersburg State University of Architecture and Civil Engineering, 4 2nd Krasnoarmeyskaya Str., Saint Petersburg, 190005, Russia, 2 Irkutsk National Research Technical University, 83 Lermontov St., Irkutsk, 664074, Russia
Abstract Signalized intersections remain among the most common elements of street and road networks and types of traffic control. This is due to the fact that traffic safety at controlled intersections largely determines road safety in cities in general. However, the Russian Federation does not have a suitable and practical method of assessing the level of safety at signalized intersections. The statistics (75 annual values of accidents) show an increase in the level of accidents at signalized intersections by several times in comparison with the figures observed in the 1980s. The authors propose an adjusted scale of levels of accidents at signalized intersections. © by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2017 2016Published The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th International Conference "Organization and Traffic Peer-review under responsibility of the organizing committee of the 12th International Conference “Organization and Traffic Safety Safety Management in large cities". Management in large cities” Keywords: Assessment of traffic safety, city controlled intersections, accident rates, relative accident rate, accident level scale
1. Introduction The relevance of the study is determined by the need to develop tools for safety assessment in urban environment. The methodology for assessing safety at signalized intersections has not been developed in our country, both in the Soviet and post-Soviet periods.
* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address:
[email protected] a*,
[email protected] b
2352-1465 © 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th International Conference “Organization and Traffic Safety Management in large cities” doi:10.1016/j.trpro.2017.01.099
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Eugene Shesterov and Alexander Mikhailov / Transportation Research Procedia 20 (2017) 613 – 617
2. Main Part Currently, the Russian Federation does not have a suitable and practical method of assessing level of safety at the signalized intersections, which are the most common types of intersections of urban main streets. The study of domestic and foreign guidelines and regulations suggests that the relative accidents rate is the most objective criterion for performing comparative analysis of signalized intersections and other intersections. In this regard, an assessment of the relative accident rate has been made based on the St. Petersburg road accident statistics. The following formula has been proposed for calculating the accident rate Ка at the intersections of rural roads [Lobanov et al (1972)]:
Ka =
A ∙ 107 ∙ Kr
(1)
(M + N) ∙ 25
where A is the number of accidents at the intersection per 1 year; Кr is the rate of annual non-uniformity of traffic, the values of which are taken depending on the month, in which a record of traffic volume Кr = 0.05–0.12 [Guidelines for Road Safety (2002)] was made; M is the traffic volume at the main road, vehicle per day, N is the same for the minor road. In the above formula the coefficient of 25 is entered to account for the average number of working days in a month, during which the traffic volume is much higher than the traffic in the weekends. Since the 1970s, an index of relative accident Ка has been used in our country to assess the safety at intersections and interchanges of motorways and became a part of the national manual ISCS 25-86 "Guidelines for Road Safety" [Highway Ministry of RF (1986)]. A grading scale of the relative accident rate has been suggested (Table 1). Table 1. Assessment of traffic safety at intersections of the rural roads Ka
12
Danger level
Not dangerous
Low danger
Dangerous
Very dangerous
Similar safety assessment indicators are used in other countries. In the US the accident rate at intersections is defined as the number of accidents attributable to 1 million of vehicles that have crossed the intersection [Massachusetts Department of Transportation (2010)].
R
A 107 365 N AADT
(2)
where A is a number of accidents at the intersection during the surveyed period; N is the duration of the period in years; 365 is the number of days in a year; AADT is an average total daily traffic through the intersection, units/h. Velues of intersections accidents rate shown on the website of Massachusetts Department of Transportation [Massachusetts Department of Transportation (2010)] are given in Table 2. Table 2. Levels of relative accident at the intersection of the state of Massachusetts, 2010 [Massachusetts Department of Transportation (2010)]. Number of accidents attributable to 1 million of vehicles that crossed intersection Signalized intersections
Unsignalized intersections
Average value
0.80
0.60
Variation range
0.76–0.92
0.43–0.68
American practice does not have this evaluation gradation shown in Table 1, but there is a concept of a Critical Crash Rate. It is defined as the accident rate that is statistically significantly different from the mean value with a confidence level of 95% or more.
Eugene Shesterov and Alexander Mikhailov / Transportation Research Procedia 20 (2017) 613 – 617
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For more than 40 years from the beginning of the use of the relative accident coefficient Ка in our country, only one study has been carried out to create the assessment scale of levels of accidents at urban signalized intersections [Mikhailov (1986)]. The calculation of Ка values at signalized intersections is produced by the following formula:
Ka =
A ∙ 107 365 ∙ kdv
(3)
where A is the number of accidents at the intersection during the year; N is total traffic at the intersection during rush hour, vehicles/h, kdv is maximum daily rate – the ratio of volume of the rush hour traffic to the daily volume, kdv = 0.09 – 0.11. Formula (3) has been proposed in view of the fact that urban conditions do not have the recommended values of intensity distribution of non-uniformity coefficients by months Кr. The gradation of levels of relative accident rates presented in Table 3 was obtained on the basis of the accounting data of accidents in the city of Leningrad at 130 controlled intersections in 1978–1980. Table 3. Classification of Signalized Intersections in Terms of Relative Accident Rate [Mikhailov (1986)]. Кav
Ка
