Appropriate Speed 

Limits for All Road Users

There is broad consensus among global roadway safety experts that speed control 

is one of the most important methods for reducing fatalities and serious injuries. 

Speed is an especially important factor on non-limited access roadways where 

vehicles and vulnerable road users mix. 

A driver may not see or be aware of the conditions within a corridor, and may 

drive at a speed that feels reasonable for themselves but may not be for all users 

of the system, especially vulnerable road users, including children and seniors. A 

driver traveling at 30 miles per hour who hits a pedestrian has a 45 percent chance 

of killing or seriously injuring them.1

 At 20 miles per hour, that percentage drops 

to 5 percent.1

 A number of cities across the United States, including New York, 

Washington, Seattle and Minneapolis, have reduced their local speed limits in 

recent years in an effort to reduce fatalities and serious injuries, with most having to 

secure State legislative authorization to do so.

States and local jurisdictions should set appropriate speed limits to reduce the 

significant risks drivers impose on others—especially vulnerable road users—and 

on themselves. Addressing speed is fundamental to the Safe System Approach 

to making streets safer, and a growing body of research shows that speed limit 

changes alone can lead to measurable declines in speeds and crashes.2

 

Applications

Posted speed limits are often the same 

as the legislative statutory speed limit. 

Agencies with designated authorities to 

set speed limits, which include States, 

and sometimes local jurisdictions, can 

establish non-statutory speed limits or 

designate reduced speed zones, and 

a growing number are doing so. While 

non-statutory speed limits must be based 

on an engineering study, conducted in 

accordance with the Manual on Uniform 

Traffic Control Devices (MUTCD) involving 

multiple factors and engineering 

judgment, FHWA is also encouraging 

agencies to use the following:3

• Expert Systems tools.

o USLIMITS2.

o NCHRP 966: Posted Speed Limit

Setting Procedure and Tool.

• Safe System approach.

Based on international experience

and implementation in the United

States, the use of 20 mph speed zones

or speed limits in urban core areas

where vulnerable users share the road

environment with motorists may result in

further safety benefits.4

Considerations

When setting a speed limit, agencies 

should consider a range of factors such 

as pedestrian and bicyclist activity, crash 

history, land use context, intersection 

spacing, driveway density, roadway 

geometry, roadside conditions, roadway 

functional classification, traffic volume, 

and observed speeds.

To achieve desired speeds, agencies 

often implement other speed 

management strategies concurrently 

with setting speed limits, such as selfenforcing roadways, traffic calming, 

and speed safety cameras. Additional 

information is in the following FHWA 

resources:

• FHWA Speed Management website.

• Self-Enforcing Roadways:

A Guidance Report.

• Noteworthy Speed

Management Practices.

• Jurisdiction Speed Management

Action Plan Development Package.

• Traffic Calming ePrimer.

FHWA-SA-21-034

1 Reducing the speed limit to 20 mph in urban areas: Child deaths and injuries would be decreased.

2 Lowering the speed limit from 30 to 25 mph in Boston: effects on vehicle speeds.

3 FHWA’s Methods and Practices for Setting Speed Limits: An Informational Report, (2012).

4 Recommendations of the Academic Expert Group for the 3rd Global Ministerial 

Conference on Road Safety.

5 https://safety.fhwa.dot.gov/speedmgt/ref_mats/fhwasa20047/sec8.cfm#foot813 

6 Safety and Operational Impacts of Setting Speed Limits below 

Engineering Recommendations.

OFFICE OF SAFETY

Proven Safety 

Countermeasures

Safety Benefits:

Traffic fatalities in the City 

of Seattle decreased 

26 percent after the 

city implemented 

comprehensive, city-wide 

speed management 

strategies and 

countermeasures inspired 

by Vision Zero. This included 

setting speed limits on 

all non-arterial streets at 

20 mph and 200 miles of 

arterial streets at 25 mph.5

One study found that 

on rural roads, when 

considering other relevant 

factors in the engineering 

study along with the speed 

distribution, setting a speed 

limit no more than 5 mph 

below the 85th-percentile 

speed may result in fewer 

total and fatal plus injury 

crashes, and lead to drivers 

complying closely with the 

posted speed limit.6 

For more information on this 

and other FHWA Proven Safety 

Countermeasures, please visit 

https://highways.dot.gov/

safety/proven-safety-counter 

measures and https://

highways.dot.gov/safety/

speed-management/ 

reference-materials.