An Assessment of Behavioral Tests to Detect Impaired Drivers
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December 1981 DOT HS-806.211 Final Report 21 An Assessment of us oep m ern <9Tranooranonf Behavioral Tests to AdwWrAs"ahm Detect Impaired Drivers K. J. Snapper D. A. Seaver J. P. Schwartz. Decision Science Consortium, Inc. 7700 Leesburg Pike, Suite 421 Falls Church, Virginia 22043 Contract No. DTNH 22-80-C-07565 Contract Amount $67,766 This document is available to the U.S. public through the National Technical information Service. Springfield, Virginia 22161 Technical Report Documentation Page . Report Me. 2. Government Acc.....n No. 3. Rec.p.ent's C.t.l.q No. DOT-HS-806 211 . Title end Svbtitl. S. Report O.,. December 1981 AN ASSESSMENT OF BEHAVIORAL TESTS TO DETECT 6. Perlora.ng o.geniset.on Code IMPAIRED DRIVERS . Perfe.n..i.q dgon.aer.on Report N.. 7. Artb.rt s) K. J. Snapper, D. A. Seaver, J. P. Schwartz* 81-11 9. Performing org.ntsett.n Nome end Address Ia. w.,b Unto Me. (TRAIS) Decision Science Consortium, Inc. 11. Contract or Great No. 7700 Leesburg Pike, Suite 421 DTNH22-80-C-07565 Falls Church, Virginia 22043 13. Type *I Roper# end Petted Covered 12. Sponsoring Agency Nome end Address Final Report U.S. Department of Transportation August 1980 - December 1981 National Highway and Traffic Safety Administration Problem Behavior Research Division 14. Sponsoring Agency Cod. Washington, D.C. 20590 15. Supplementary Notes .*With a contribution by Elliot R. Levine, Esq. 16. Abstract ' This study was conducted to assess the feasibility and practicality of road side behavioral tests for driving impairment. Such tests are seen as complementary to chemical tests of blood drug concentration. Methodological issues in the use of behavioral tests are identified and discussed focusing specifically on the validity of behavioral measures. It is argued that if validity is defined as pre dicting accidents, it will always be low for any behavioral test as well as for chemical tests because of the inherent unpredictability of accidents. The rationale for using behavioral tests, particularly a battery of behavioral tests, to detect driving impairment is, then, that such tests can measure the level of behavioral skills involved in driving. In order to evaluate various behavioral tests, a large literature was reviewed to identify potential tests and any previous studies of them. Criteria for evaluating the tests were developed, including validity, reliability, ease of operational use, safety, and diagnosticity. Each of 54 tests were scored on each criterion, and criteria were weighted by their relative importance from the perspectives of researchers and users to produce an overall index of the feasibility of each test. Tests that were rated highly include visual acuity, finger-to-finger, finger-to-nose, and romberg (and modified romberg). An analysis was also performed of legal issues relating to the use of roadside be havioral tests. Such tests appear to have useful status as evidence (primarily circumstantial), and probably can be used without a need for expert witnesses. 17. Key words It. Distribution Statement Legal Issues Test Validity Document is available to the public Behavioral Tests Test Reliability through the National Technical Inf Driving Impairment Test Safety oration Service, Springfield, Virginia Human POperationalPerformanceer Use of Drug Effects Test 22161 20. S.ctrrity Cl.ssil. (.f this peg.) 21. No. of Pages 1 22. Pr's. 19. 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CI),51.1.4. .c 11 METRIC CONVERSION FACTORS * TABLE OF CONTENTS Page 1.0 INTRODUCTION AND BACKGROUND ................................... 1-1 1.1 Legislative Mandate for Study ............................ 1-1 1.2 Technical Problems in Developing Tests of impairment ..... 1-2 1.2.1 Non-Invasive Chemical Tests ....................... 1-3 1.2.2 Ambiguity of Blood Drug Concentration Analyses .... 1-3 1.2.3 Defining Impairment Threshold in Terms of BDC ..... 1-4 1.2.4 Specificity of Behavioral Tests ................... 1-4 1.2.5 Practicability .................................... 1-5 1.3 Scope of Present Study: Assessment of Behavioral Test Procedures .......................................... 1-5 2.0 IMPAIRMENT MEASURES: METHODOLOGICAL ISSUES IN INDEX CONSTRUCTION, EVALUATION, AND VALIDATION ...................... 2-1 2.1 The Criterion Problem .................................... 2-i 2.2 Operational Criteria ..................................... 2-3 2.2.1 Traffic Accidents as an Operational Criterion of Impairment ..................................... 2-3 2.2.2 A Behavioral Test as an Operational Criterion of Impairment ..................................... 2-5 2.2.3 Driving-Like Tasks as an Operational Criterion of Impairment ..................................... 2-7 2.2.4 BDC as an Operational Criterion of impairment 2-9 2.3 Some Tenets Regarding Development of Measures of Impairment ............................................... 2-11 2.4 Procedures for the Development of a Behavioral Index of Impairment ............................................ 2-13 2.5 Validation of a Behavioral Index of Impairment ........... 2-18 2.6 Criteria for Evaluating Indices of Impairment ............ 2-18 3.0 CRITERIA, TESTS, AND EVALUATION ............................... 3-1 3.1 Evaluation Approach and Methodology ...................... 3-2 3.2 Development of Evaluative Criteria ....................... 3-5 3.3 identification of Behavioral Tests ....................... 3-10 3.4 Evaluation of Behavioral Tests ........................... 3-27 3.4.1 Importance Weights for Criteria ................... 3-27 3.4.2 Comparative Assessments of Tests .................. 3-32 3.5 Quantitative Evaluation Results .......................... 3-42 4.0 DISCUSSION AND RECOMMENDATIONS ................................ 4-1 5.0 REFERENCES ...................................................... 5-1 iii TABLE OF CONTENTS (continued) Page APPENDIX: ANALYSIS OF LEGAL ISSUES (Elliot R. Levine, Esq.) ....... .A-1 A..1 Summary ................................................. A-1 A.1.1 Legal Relevance of Behavioral Tests ..... ....s. A-1 A.1.2 Evidential Role of Behavioral Tests .............. A-1• A.1.3 Police Officers.as Witnesses ...................... A-1 A.1.4 Constitutional Rights .............................. A-2 A.1.5 Due Process ................................. A-3 A.1.6 Indigent Defendants A-3 A.2 Legal Relevance of Field Behavior Tests A-3 A.3 Behavioral Tests as Evidence ............................ A-4 A.3.1 Difference Between Circumstantial and Direct Evidence ..................... .......... A-4 A.3.2 Behavioral Tests are Circumstantial Evidence .......................................... A-4 A.3.3 Sufficiency of Circumstantial Evidence ........... A-5 A.3.4 Requirements for Direct Evidence A-5 A.3.5 Effects of Distinction Between "Narcotic" and Other Drugs .................................. A-8 A.4 Police Officers as Witnesses ............................ A-9 A.4.1 Police Officers as Non-Experts ................... A-9 A.4.2 Constraints on Testimony .......................... A-10 A.5 Constitutional Rights and Behavioral Tests .............. A-11 A.5.1 Right to Remain Silent ............................ A-il A.5.2 Use of Force ..................................... A=12 A.5.3 Behavioral Tests Without Counsel A-13 A.5.4 Refusal to Submit to Behavioral Test may be Used Against Defendant ........................ A-13 A.5.5 Implied Consent and Behavioral Tests .............. A-13 A.6 Blood Tests in Addition to Behavioral Tests ............. A-14 A.7 Rights of Indigents ..................................... A-17 A.8 Conclusion ........................................ A-18 iv 1.0 INTRODUCTION AND BACKGROUND Drivers who are unable to operate their vehicles safely should not drive, but there is considerable controversy about how best to detect driver impairment.