Objectives: This paper aimed to (i) differentiate the effects of contributory factors on crash risks related
Received 29 June 2016 to different transportation modes, i.e., motor vehicle, bicycle and pedestrian; (ii) explore the potential
Received in revised form 9 October 2016 contribution of zone-level factors which are traditionally excluded or omitted, so as to track the source
Accepted 13 October 2016 of heterogeneous effects of certain risk factors in crash-frequency models by different modes.
Methods: Two analytical methods, i.e. negative binomial models (NB) and random parameters negative
Keywords: binomial models (RPNB), were employed to relate crash frequencies of different transportation modes to
Transportation modes
a variety of risk factors at intersections. Five years of crash data, traffic volume, geometric design as well
Macroscopic variables
Unobserved heterogeneity as macroscopic variables at traffic analysis zone (TAZ) level for 279 intersections were used for analysis
Buffer width as a case study.
Intersection safety Results: Among the findings are: (1) the sets of significant variables in crash-frequency analysis differed for
different transportation modes; (2) omission of macroscopic variables would result in biased parameters
estimation and incorrect inferences; (3) the zonal factors (macroscopic factors) considered played a more
important role in elevating the model performance for non-motorized than motor-vehicle crashes; (4) a
relatively smaller buffer width to extract macroscopic factors surrounding the intersection yielded better
estimations.
Objectives: This paper aimed to (i) differentiate the effects of contributory factors on crash risks related Received 29 June 2016 to different transportation modes, i.e., motor vehicle, bicycle and pedestrian; (ii) explore the potential Received in revised form 9 October 2016 contribution of zone-level factors which are traditionally excluded or omitted, so as to track the source Accepted 13 October 2016 of heterogeneous effects of certain risk factors in crash-frequency models by different modes. Methods: Two analytical methods, i.e. negative binomial models (NB) and random parameters negative Keywords: binomial models (RPNB), were employed to relate crash frequencies of different transportation modes to Transportation modes a variety of risk factors at intersections. Five years of crash data, traffic volume, geometric design as well Macroscopic variables Unobserved heterogeneity as macroscopic variables at traffic analysis zone (TAZ) level for 279 intersections were used for analysis Buffer width as a case study. Intersection safety Results: Among the findings are: (1) the sets of significant variables in crash-frequency analysis differed for different transportation modes; (2) omission of macroscopic variables would result in biased parameters estimation and incorrect inferences; (3) the zonal factors (macroscopic factors) considered played a more important role in elevating the model performance for non-motorized than motor-vehicle crashes; (4) a relatively smaller buffer width to extract macroscopic factors surrounding the intersection yielded better estimations.
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