Keith Vodden Dr. Douglas Smith - Transports Canada

Appendix A—Detail on Calculations of the Ontario Model
we use an analysis by Mary Chipman 1 of the 1990 Ontario Health Survey. No more
recent study exists to help estimate the number of minimal injuries. However, given the
age of the study one of the adjustments we make is to reflect the changed mix of injuries
from motor vehicle collision in 2004 compared to 1990.
We make a number of adjustments in the Chipman analysis to fit the needs of the
social cost model. In brief these adjustments:
• Adjust the proportion of injuries to pedestrians and cyclist to reflect the mix in
motor vehicle collisions. The 1990 Ontario Health Survey used a broader
definition of traffic collision that did not need to involve a motor vehicle.
• Reduce the number of emergency room visits by 10% to estimate minor injuries.
This reflects the proportion that becomes major injuries (hospital stays). Using
estimates from the 1990 Ontario Health Survey of emergency room and hospital
room use without adjustment would lead to double-counting otherwise.
• Calculate minimal injuries as a residual by subtracting major and minor injuries
from total injuries.
• Adjust for the changing mix of injury severities between 1990 and 2004 motor
vehicle collisions.
The following adjustments were made 2 :
• Reduce injuries to pedestrians and cyclists to reflect the proportions of injuries in
motor vehicle collisions recorded in ORSAR for 1990 (vehicle occupants, 90.6%;
pedestrians, 5.8%; and cyclists, 3.6%) 3 compared to Chipman (vehicle occupants,
67.7%; pedestrians, 17.4%; and cyclists, 14.9%). The 1990 Ontario Health Survey
did not require involvement of a motor vehicle in its definition of a traffic
collision. This adjustment brings the Chipman data in line with our definition of a
motor vehicle collision.
• Estimate the number of minor injuries by reducing the estimated number of
emergency room visits by 90% of the number of hospital admissions. This reflects
information obtained in the 1994 Social Cost study for the per cent of hospital
admissions that go through the emergency department. (For 2004, the percentage
derived from MOH&LTC is 85%.)
• Estimate the number of minimal injuries as the residual left by subtracting major
and minor injuries from the number of total injuries estimated in the analysis.
1 Chipman, Mary L., "Health Service Use Attributable to Injury in Traffic Crashes: Data from a Population
Survey," 36th Annual Proceedings, Association for the Advancement of Automotive Medicine, October
5-7, 1992, Portland, Oregon.
2 More detail on these adjustments can be found in the previous (1994) Social Cost Study.
3 From the 2004 ORSAR data the proportions are very similar (vehicle occupants, 89.7%; pedestrians,
6.4%; and cyclists, 3.9%).
TNS Canadian Facts, Social and Policy Research 119