Speed Limit Fact Sheet ( PDF )
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The Effects of Raising and Lowering the Speed Limit
This report, which was prepared for the Federal Highway Administration, examines the effects of raising and lowering posted speed limits on driver behavior for urban and rural nonlimited access highways.

Speed Limits – When and Why the 85th Percentile, and how it relates to safety, enforcement and our laws
A presentation by Chad Dornsife, Executive Director, Best Highway Safety Practices Insitutute, at the 2009 Institute of Transportation Engineers District 6 meeting.

Disinformation Campaign on the Effects of Lowering Urban Speed Limits
The Insurance Institute for Highway Safety published a report saying that lowering Boston posted limits from 30 to 25 mph reduced overall traffic speed. Except that’s not what their data showed; there was virtually no change in travel speeds. Dropping the speed limits creates more technical violators, more speeding citations, and gives auto insurance companies — the IIHS’s funding source — more opportunities to raise premiums.

Speed Zoning Synthesis, a USDOT study
This study reviews the principles and practices used to set speed limits. It is based mainly on a survey of traffic officials conducted by the American Association of State Highway and Transportation Officials (AASHTO).

Do crash rates really increase with increases in average speed?
This study by John McKerrall Lambert reviews research on crash rates by road type and speed limits, and finds no correlation between crash rates and average speeds.

Did the Higher 65 MPH Speed Limit Actually Reduce Highway Deaths?
In 1987, many states raised the maximum speed limtis from 55 to 65 mph on portions of their rural interstate highways. This press release summarizes the findings of a AAA-funded study conducted by Dr. Charles Lave.

Speed Doesn’t Kill: The Repeal of the 55-mph Speed Limit
This study by the Cato Institute shows that, despite dire predictions by “safety” advocates, the repeal of the 55-mph National Maximum Speed Limit didn’t result in more deaths.

Did Raising Freeway Speed Limits Affect Traffic Safety?
This study analyzes state-by-state fatality data published by the National Highway Traffic Administration derived from the Fatal Analysis Reporting System and Federal Highway Administration statistics.

Comparison of Speed Zoning Procedures and Their Effectiveness
This report describes the findings of a study conducted to determine if including factors in addition to the 85th percentile speed could increase the effectiveness of Michigan’s speed zoning procedure.

A Recommended Speed Zoning Practice
A proposal for speed zoning practices from the Institute of Transportation Engineers.

New York DOT Study
This press release from the New York Governor’s Office highlights the findings of research on raising speed limits in that state. It shows that actual travel speeds stayed the same despite the speed limit increase.

New Jersey Speed Limit Report
This three-year study by the New Jersey Department of Transportation looks at the state’s 65-mph speed limit. The analysis supports expanding the 65-mph speed limit.

An Evaluation of the Michigan 70 MPH Speed Limit
On August 1, 1996, the speed limit on certain sections of Michigan freeways increased from 65 MPH to 70 MPH. A preliminary accident analysis was performed on the control and test sections to determine the effect of increasing the speed limit on accidents. It was proved that increasing the speed limit on certain sections of freeway in Michigan had little effect on the change in speed and capacity on both test and control sections.

Traffic Safety Impact Of 1995-1996 Increases In California’s Speed Limits
Excerpt: “There is no evidence that increased speed limits in California compromised the general level of traffic safety in the state. […] What this study’s conclusion should be interpreted to mean is that California’s policy of raising speed limits (on roadways where higher limits were warranted) did not result in an overall increase in fatal and injury crashes.”

Driver Speed Behavior on U.S. Streets and Highways
Excerpt: “Properly established speed limits foster voluntary compliance and separate the occasional high-risk driver from the vast majority of drivers. On the other hand, speed limits which are set artificially low tend to be ignored and misallocate resources, apprehending and prosecuting motorists driving at safe speeds. Over time this could lead to a loss of respect for all speed limits and create the impression that traffic law enforcement and the judicial system are unfair.”

Evaluation of Lower Speed Limits on Urban Highways
A study from the University of Nebraska. Excerpt: “The results of the analysis of the accident experience in speed zones indicate that zones with posted speed limits equal to the reasonable speed limits proposed by the NDOR method of speed zoning are safer than zones with posted speed limits that are 5 and 10 mph below the reasonable speed limits.”