title: Effectiveness of traffic management in Salt Lake City, Utah.
abstract: OBJECTIVE
  The effectiveness of speed humps, 14 ft (4.3 m) wide by 3.5 in (8.9 cm) high, and tables, 22 ft (6.7 m) wide, on 12 streets in Salt Lake City, Utah was investigated. Mean and 85th percentile spot speeds, speed limit compliance, motor-vehicle crashes, and resident opinions were considered.
  
  
  METHODS
  Spot speeds were collected at 18 "between-hump" locations. Motor-vehicle crash data were obtained for "before" and "after" periods of equal duration. A total of 436 residents were surveyed; 184 responded.
  
  
  RESULTS
  The mean and 85th percentile speeds decreased at 14 and 15 locations, respectively. The average reduction in the 85th percentile speed (3.4 mph or 5.4 km/h) was significant in flat and rolling terrain, but not on uphill or downhill segments. The number of sites with 50% speed limit compliance increased from 4 to 12. The number of motor-vehicle crashes decreased from 10 to 9; the change was not significant, but injury crashes decreased from five to one. Regarding the residents, 30% were positive, 25% were negative, and 45% offered suggestions, some of which were conflicting.
  
  
  CONCLUSIONS
  Further study is needed on speed hump spacing and speed tables in hilly terrain. Example results should be shared with residents to inform their decision-making.
  
  
  CONCLUSIONS
  At least 78% of the sites experienced a decrease in the mean or 85th percentile speed, or an increase in speed limit compliance.
  
  
  CONCLUSIONS
  These findings should be useful to agencies that are planning or implementing traffic calming projects, and to analysts.
authors.affiliation: Civil Engineering Department, 3801 West Temple Avenue, California State Polytechnic University, Pomona, CA 91768-2557, USA. wdcottrell@csupona.edu
authors.forename: Wayne D
authors.initials: WD
authors.lastname: Cottrell
authors.forename: Naree
authors.initials: N
authors.lastname: Kim
authors.forename: Peter T
authors.initials: PT
authors.lastname: Martin
authors.forename: H Joseph
authors.initials: HJ
authors.lastname: Perrin
mesh_terms: D000054:Acceleration; D000056:Accident Prevention / Q000379:methods*; D000063:Accidents, Traffic / Q000517:prevention & control* / Q000639:trends; D003625:Data Collection; D006801:Humans; D015397:Program Evaluation; D014589:Utah