MUTCD
Standards on Speed Limits
from
the Manual on Uniform Traffic Control Devices (MUTCD)
http://mutcd.fhwa.dot.gov/
Section
2B.13 Speed Limit Sign (R2-1)
Standard:
After an engineering study has been made in accordance with established
traffic engineering practices, the Speed Limit (R2-1) sign (see
Figure 2B-1) shall display the limit established by law, ordinance,
regulation, or as adopted by the authorized agency. The speed limits
shown shall be in multiples of 10 km/h or 5 mph.
Guidance:
At least once every 5 years, States and local agencies should reevaluate
non-statutory speed limits on segments of their roadways that have
undergone a significant change in roadway characteristics or surrounding
land use since the last review.
No
more than three speed limits should be displayed on any one Speed
Limit sign or assembly.
When
a speed limit is to be posted, it should be within 10 km/h or 5
mph of the 85th-percentile speed of free-flowing traffic.
Option:
Other factors that may be considered when establishing speed limits
are the following:
- Road characteristics,
shoulder condition, grade, alignment, and sight distance;
- The pace
speed;
- Roadside
development and environment;
- Parking practices
and pedestrian activity; and
- Reported
crash experience for at least a 12-month period.
Two
types of Speed Limit signs may be used: one to designate passenger
car speeds, including any nighttime information or minimum speed
limit that might apply; and the other to show any special speed
limits for trucks and other vehicles.
A
changeable message sign that changes the speed limit for traffic
and ambient conditions may be installed provided that the appropriate
speed limit is shown at the proper times.
A
changeable message sign that displays to approaching drivers the
speed at which they are traveling may be installed in conjunction
with a Speed Limit sign.
Guidance:
If a changeable
message sign displaying approach speeds is installed, the legend
YOUR SPEED XX km/h (MPH) or such similar legend should be shown.
The color of the changeable message legend should be a yellow legend
on a black background or the reverse of these colors.
Support:
Advisory Speed signs are discussed in Sections 2C.36 and
2C.46 and Temporary Traffic Control Zone Speed signs are discussed
in Part 6.
Section
2B.03 Size of Speed Limit Signs
Standard:
The
Speed Limit Sign (R2-1) shall be 24” by 30” unless conditions warrant
a larger sign which can be 36” by 48” or 48” by 60”.
Option:
The
Oversized size may be used for those special applications where
speed, volume, or other factors result in conditions where increased
emphasis, improved recognition, or increased legibility would be
desirable.
Section
2B.18 Location of Speed Limit Signs
Standard:
Speed Limit (R2-1)
signs, indicating speed limits for which posting is required by
law, shall be located at the points of change from one speed limit
to another.
At
the end of the section to which a speed limit applies, a Speed Limit
sign showing the next speed limit shall be installed. Additional
Speed Limit signs shall be installed beyond major intersections
and at other locations where it is necessary to remind road users
of the speed limit that is applicable.
Speed
Limit signs indicating the statutory speed limits shall be installed
at entrances to the State and at jurisdictional boundaries of metropolitan
areas.
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