EXECUTIVE
SUMMARY
This report defines
the problem of lane change crashes in the United States (U.S.)
based on data from the 1999 National Automotive Sampling System/General
Estimates System (GES) crash database of the National Highway
Traffic Safety Administration. The results from this analysis
provide a basis for related future research in the U.S. Department
of Transportation’s Intelligent Vehicle Initiative to
solve traffic safety problems through the development and deployment
of vehicle-based and vehicle-infrastructure cooperative countermeasure
systems using advanced technologies. Lane change crashes (or
more properly, the lane change family of crashes) are defined
in this report as two-vehicle crashes that occur when one vehicle
encroaches into the path of another vehicle initially on a parallel
path with the first vehicle and traveling in the same direction.
Such encroachment results from various vehicle maneuvers including
typical lane change, merge, pass, drift, turn, and leave or
enter a parking position. There were 539,000 twovehicle lane
change crashes in 1999 based on GES data, or about 9% of all
police-reported motor vehicle crashes. This report breaks down
these crashes into major pre-crash scenarios and describes the
characteristics of each scenario in terms of vehicle types involved,
physical setting, crash contributing factors, and injury severity.
Lane change crashes
mostly consist of the following seven pre-crash scenarios, ranked
in a descending order in terms of their frequency of occurrence
in 1999:
- Two vehicles on
parallel paths; one intentionally changes lanes and collides
with other vehicle: 207,000 (typical lane change).
- Two vehicles on
parallel paths; one turns across the path of the other at
a roadway junction: 89,000 (turning at junction).
- Two vehicles on
parallel paths (both going straight/both turning left/both
turning right/both negotiating curve); one drifts into another’s
lane with no apparent reason: 62,000 (drifting).
- Two vehicles on
parallel paths; one turning at a roadway junction and one
passing: 46,000 (turning combined with passing).
- Two vehicles on
parallel paths; one moves into the other’s lane to pass
the other, or to pass a third vehicle: 27,000 (passing).
- One vehicle leaves
parked position and sideswipes/is sideswiped by another vehicle
in lane into which the first vehicle is trying to merge: 25,000
(leaving parked position).
- One vehicle merges
into the lane of another from entrance to limited access highway
and/or other similar entrance, and sideswipes/is sideswiped
by the other vehicle: 19,000 (merging).
The seven most common
pre-crash scenarios accounted for about 88% of all two-vehicle
lane change crashes. A large share (10%) of “typical lane
change” crashes involved large trucks (medium and heavy
trucks) changing lanes and light vehicles (passenger cars, sport
utility vehicles, vans, and pickups) going straight; in contrast,
about 5% of these crashes involved the reverse combination.
Similarly, trucks were turning and light vehicles were going
straight in 10% of the “turning at junction” crashes;
however, the reverse combination was reported in only 1% of
these crashes. The highest involvement of trucks was observed
in the “merging” scenario, accounting for 42% of
these crashes. Buses (transit and inter-city buses, not school
buses) were mostly associated with in “drifting”
and “leaving parked position” scenarios.
The physical setting
of the seven scenarios was described in terms of the number
of travel lanes per direction of travel, crash relation to junction,
posted speed limit, roadway alignment, and roadway profile.
Moreover, this report examined the factors that might have contributed
to the crash in each of the seven scenarios using available
GES variables. The list of factors included driver distraction,
vision obstruction, speeding, traffic violation, hit and run,
and environmental factors such as night and adverse weather
conditions. Finally, the maximum injury severity per crash was
analyzed which revealed that 14% of lane change crashes resulted
in some form of injury.
The
Full Report is available for download in PDF. The size is 261K
and is 52 pages.
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