2. Evaluation of Physical and Mental (P&M) Factors

  • Comprehensive policy analysis. In 1978, R&D, in cooperation with the Division of Drivers Licensing, produced a report (Research Report No. 67) in response to SB 2033. This bill required the department to conduct an evaluation of the fairness and validity of its licensing policy concerning drivers with physical or mental (P&M) medical conditions. Numerous policy changes were initiated as a result of that investigation. One of the more notable changes from a benefit-cost standpoint concerned the type of probation action used for drivers with certain conditions. Prior to that time the department, when deciding to license P&M drivers on a probationary basis, required the submittal of periodic reports from a physician as a condition of probation. Since this form of probation is costly to DMV, the physician, and the driver, R&D designed an experiment comparing the traffic safety value of medical probation with two alternatives that did not require such reports. Each of the less costly alternative programs was essentially equal to the standard medical probation in terms of subsequent accidents. The department decided to replace the medical probation with the alternative consisting of probation without periodic medical reports for most P&M cases. This policy was abandoned in 1988 due to program management concerns over maintaining appropriate medical control and treatment in absence of a periodic physician-report requirement. (see footnote 3) Based on the benefit-cost analysis in the original study, it is estimated that the less expensive probation process saved the department approximately 2 million dollars during the period 1979-1987.
  • Accident risk of deaf drivers, bioptic lens wearers, and physically handicapped drivers. R&D has conducted statistical studies of the above populations. Two studies of deaf drivers, published in 1963 and 1964 (Research Report Nos. 15 and 16), provided evidence that, under certain conditions, totally deaf drivers represented higher-than-average accident risks. These studies, which constitute the only known empirical evidence on the role of deafness in driving, have been used several times by the Federal Bureau of Motor Carrier Safety to successfully rebut legal challenges to its policy of not allowing deaf persons to drive commercial vehicles in interstate commerce. In 1973, R&D conducted a study of the driving records of drivers with limb disabilities (amputees, paraplegics, drivers with cerebral palsy, etc.). This study (Research Report No. 42), requested by a California legislator, found that drivers with such handicaps have driving records as good or better than those of non-disabled drivers. These results supported DMV's long-standing policy of licensing drivers with non-progressive disorders, licensing being based solely on their ability to demonstrate adequate knowledge and skill on the written and driving test. It has also been cited by groups involved in promoting non-discriminatory liability insurance rates for the disabled.

The first study on visually-impaired drivers wearing bioptic telescopic lenses ("bioptics") was completed by R&D in 1983 (Research Report No. 86). Although opinion has been divided on the driving safety of bioptic drivers and most states do not permit low-vision drivers to qualify with bioptic lenses, California has licensed bioptic drivers for several years, considering each case on an individual basis. In an effort to establish the safety impact of this policy, DDSL requested R&D to conduct a statistical analysis of the driving records of identified bioptic users, the study mentioned above.

The initial report was based on an analysis of several hundred drivers, and indicated that bioptic drivers have significantly higher accident rates, including injury and fatal accidents, than do drivers of similar age with "normal" vision. The original report contains a number of recommendations for reducing this negative impact, some of which were implemented. These changes included a greater use of license restrictions and the scheduling of reexaminations upon receipt of any accident report involving bioptic drivers.

A very recent evaluation (Research Report No. 163, 1996) by R&D of all currently licensed bioptic drivers shows that bioptic lens wearers continue to have substantially elevated accident rates and that many are not appropriately restricted. The policy implications of this latter study are currently under review.

R&D has also recently completed a study of the department's policy of requiring drivers who cannot pass the standard DMV road test, or who have certain medical conditions, to pass a special drive test (SDT) in order to be licensed. The results of this study (Research Report No. 160) indicate that those who pass the SDT have subsequent accident rates that are 3 times higher than those of "normal" drivers of the same age and gender. The report concludes that the current SDT does not effectively screen out high-risk drivers and that the testing policy, test scoring criteria, and the test itself should be revised. This report has resulted in major changes in the structure of the SDT system and the criteria for determining SDT referral.

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