WHEN DID A REDUCED SPEED LIMIT SHOW AN EFFECT? EXPLORATORY IDENTIFICATION OF AN INTERVENTION TIME
In a statistical analysis of accident data before and after a speed limit reduction, the time of the countermeasure is, of course, well known. Our understanding of the accident process may, however, be increased if we assume in a thought experiment that this time is unknown. We ask if the data themselves can tell us something about such a possible time. By means of time series of traffic accidents in Zurich before and after a speed limit reduction, different exploratory methods are presented to identify the "unknown" time of this measure. For most of the investigated series, the most likely time was found to lie in the three months before the true introduction. A possible explanation of this result may be that the media already informed the public before the countermeasure was actually introduced. This finding leads to an improved parsimonious intervention model which distinguishes between a possible "preintervention effect" and the usual "intervention effect."
-
Availability:
- Find a library where document is available. Order URL: http://worldcat.org/issn/00014575
-
Corporate Authors:
Pergamon Press, Incorporated
Headington Hill Hall
Oxford OX30BW, -
Authors:
- Helfenstein, U
- Publication Date: 1990-2
Media Info
- Features: Figures; References;
- Pagination: p. 79-87
-
Serial:
- Accident Analysis & Prevention
- Volume: 22
- Issue Number: 1
- Publisher: Elsevier
- ISSN: 0001-4575
- Serial URL: http://www.sciencedirect.com/science/journal/00014575
Subject/Index Terms
- TRT Terms: Before and after studies; Crashes; Driver rehabilitation; Speed limits; Statistical analysis; Time
- Uncontrolled Terms: Intervention
- Old TRIS Terms: Time factor
- Subject Areas: Data and Information Technology; Highways; Operations and Traffic Management; Safety and Human Factors;
Filing Info
- Accession Number: 00492293
- Record Type: Publication
- Report/Paper Numbers: HS-040 795
- Files: HSL, TRIS, ATRI
- Created Date: Mar 31 1991 12:00AM