Summary of other studies on the effect of altering speed limits


#S = Number of Sections
B = Before
A = After
AL = After Posting Lower Limit
AH = After Posting Higher Limit
Author, Date Speed Limit Average 85th Percentile Speed
Location #SBA BALAH Remarks
Urban
St. Paul, Minnesota Avery, 1960 7 30 35 35.5 35.8 Compliance increased from 36 to 80 percent.
4 30 40 39.4 40.8 Compliance increased from 19 to 82 percent.
 
West Lafayette, Indiana Elmberg, 1960 1 35 30 38.4 38.5 Percentage of vehicles exceeding the speed limit by 5 mi/h or more increased from 10 to 38 percent.
 
St. Joseph Ogawa, 1962 1 30 35 30.6* 31.3* Speed limit revisions based on 85th percentile speeds. The mean speed increase in Orden is statistically significant.
Orden 1 40 35 32.2* 33.3*
Fithian, Illinois 1 35 40 34.9* 35.3*
 
Columbia, South Carolina Roberts, 1967 1 35 40 42.5 41.0 Compliance increased from 28 to 75 percent
 
10 California Cities Spitz, 1984 40 NA NA 39.9 40.3 The 85th percentile speed in the 27 comparison samples where no change in the limit was made increased from 40.1 to 40.8 mi/h.
10 NA NA 36.9 38.6
 
3 Urban Fringe Areas in Texas Dudek, 1986 6 55 45 55.9 54.0 Lowering the speed limit had little effect on vehicle speeds and speed variance
 
Rural
Illinois Kessler, 1959 30 30 40 38.9 38.4 Driver compliance increased from 39 to 85 percent.
 
Houston District, Texas Rowan, 1962 1 60 55 55.5 55.0 Speed limits were established in the after periods based on the 85th percentile speeds. A slight increase in the dispersion of speeds was reported after the new limits were established
1 60 50 53.7 52.0
1 60 45 47.3 46.4
1 60 40 41.5 39.9
1 60 35 40.2 38.9
1 60 30 31.2 33.2
Paris District, Texas 1 60 55 55.2 51.2
1 60 50 51.5 59.9
1 60 45 47.6 43.9
1 60 40 40.4 38.6
1 30 55 53.2 50.5
1 30 50 52.6 51.3
1 30 45 45.4 45.2
1 30 40 40.3 42.0
1 30 35 36.8 38.4
 
Operational studies
Massachusetts Oct. 1966 19
2-lane
30-45 20-35 47.5 48.3 After posting 10mi/h lower and higher limits than existing zones, no differences in 85th percentile speed were found
30-45 40-55 48.0
6
d-lane
50-55 40-45 60.7 60.3
60-65 60.7 61.0
 
Minnesota Jan. 1979 12
2-lane
45 30 NA 43.6
4
4-lane
40 30 42.0 40.3
 
Washington 1981-82 3 25 30 34.7 34.3
1 50 55 57.0 59.0
1 50 35 43.0 42.0
3 40 35 45.0 43.7
 
Michigan 1982 4 25 35 37.6 36.0 Compliance increased from 10 to 81 percent.
4 55 50 56.8 54.8 Compliance decreased from 73 to 56 percent.
4 55 50 57.8 56.0 Compliance decreased from 71 to 46 percent.
5 45 35 49.2 47.0 Compliance decreased from 56 to 7 percent.
NA = Not Available
* = Denotes mean speeds, not 85th percentile speeds


Source: Effects of Raising and Lowering Speed Limits, Final Report. FHWA-RD-92-084

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