Barbara M. Stepanski, MPH; Leslie Upledger Ray, MA, MPPA; Patricia Murrin, RN, MPH; Jan Pierce
This investigation of drivers over 54 years old involved in injury crashes during FY 96/97 presents a practical application of ArcView GIS and spatial analysis in injury surveillance and prevention. Emergency Medical Services Prehospital Patient Records (PPR) and SWITRS crash records were examined. Rates for drivers in crashes and drivers who were at fault were highest in the youngest age groups (16-19, 20-24) and lowest in the 55-64 and 65-74 year olds. Although the 85+ age group had the 3rd highest rates, they represent a small percentage of drivers on the road. These findings contradict recent reports on elderly drivers.
Recent reports have indicated that older drivers, those 55 years old and older, have a higher motor vehicle injury crash rate and experience more severe injuries in such crashes. In addition, it is predicted that the 55 and older population will increase by 118% by the year 2020. Therefore, investigators examined the San Diego County Emergency Medical Service (EMS) Prehospital records and the Statewide Integrated Traffic Records System (SWITRS) for fiscal year 96/97 to determine local trends of injury crashes in this age group. EMS data consists of emergency calls in which paramedics or emergency medical technicians were dispatched to a patient. The SWITRS database consists of countywide injury crashes as reported by local law enforcement to the California Highway Patrol. Data were analyzed by age group, gender, ethnicity, community, estimated hour of incident, Prehospital run outcome, vehicle restraint use, and party at fault.
SWITRS data, which contained location data for each crash, was received from the California Highway Patrol as a fixed-format ASCII file. This file was then converted, using SPSS for Windows, into a dBase format so that ArcView could read it. Dot maps were produced using SWITRS data. Approximately 80% of incidents were automatically geocoded using a data matching program developed specifically for this purpose. The remaining 20% were geocoded using narrative information.
In FY 96/97, 1098 Prehospital patients age 55+ were motor vehicle/motorcycle drivers involved in an injury crash. Thirty-nine percent of these drivers were 55-64 years old, 30.3% were 65-74, 23.8% were 75-84, and 6.9% were 85+. Approximately one-third of the injury crashes occurred in only 4 of the 63 communities in the county. The majority of the drivers were males and White, 52% and 65% respectively. The analysis of estimated hour of incident revealed that most injury crashes occurred between 11:00 a.m. and 4:00 p.m. Patient status became more serious as age increased, with overall percentages of 78.1% mild, 15.4% moderate and 5.4% acute. Of the 1098 victims in this age group, 30 were operating motorcycles. Of these motorcycle drivers 73.3% were wearing a helmet and 10.0% were wearing full protective gear. Sixty-one percent of motor vehicle drivers had lap and shoulder restraints on while only 4% were unrestrained. SWITRS data indicated that the major violations were Auto Right-of-Way, Unsafe Speeds, and Traffic Signals and Signs. Compared to all nine age groups, rates of incidence for 55 and older drivers ranked 8th (55-64), 9th (64-74), 6th (75-84), and 3rd (85+)(see Figure 1) However, higher percentages of the oldest drivers were found to be at fault (85+:81%, 75-84:61%), and the 55-64 and 65-74 year olds at fault percentages were lower than those of the youngest drivers (16-19:60%, 20-24:51%).
Low rates and at fault percentages for the 55-64 and 65-74 age groups were found to contradict recent reports. Other than the 85+ age group having the 3rd highest injury crash rate and the highest percentages of at fault violations, the youngest drivers (16-19 and 20-24) are were found to be the highest risk age groups. The injury crash rate for the youngest age group more than doubles the rate for the 85+ age group. In addition, the 85+ age group had a higher percentage of acute status, however this result was not significant.
A limitation of this study is that it was not possible to calculate rate of crash per mile by age with the current data. Injury crash rates were calculated with the total number of drivers per age group. However, this is appropriate for assessing the impact of drivers in this age group on the population in terms of crashes.
In light of these results, efforts towards reverse graduated licensing and mandatory surrendering of a license at a certain age may want to be revisited. The costs and benefits must be weighed; the loss of independence (possibly resulting in isolation and depression) against the real threat that older drivers pose on the road. Results of this analysis support the need to focus efforts of safe driving programs on young drivers.
Barbara Stepanski email bstepahe@co.san-diego.ca.us
Biostatistician, County of San Diego, Health and Human Services Agency, Division of Emergency Medical Services
6255 Mission Gorge Rd., San Diego, CA 92120, phone (619)285-6429, fax (619)285-6531