Objectives: This paper aimed to (i) differentiate the effects of contributory factors on crash risks related
to different transportation modes, i.e., motor vehicle, bicycle and pedestrian; (ii) explore the potential
contribution of zone-level factors which are traditionally excluded or omitted, so as to track the source
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
binomial models (RPNB), were employed to relate crash frequencies of different transportation modes to
a variety of risk factors at intersections. Five years of crash data, traffic volume, geometric design as well
as macroscopic variables at traffic analysis zone (TAZ) level for 279 intersections were used for analysis
as a case study.
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