Legislative Analysis
Phone: (517) 373-8080
DETERMINING MODIFIED SPEED LIMITS
http://www.house.mi.gov/hfa
House Bill 4733 (H-1) as referred to second committee Analysis available at
Sponsor: Rep. Bradley Slagh http://www.legislature.mi.gov
1st Committee: Transportation
2nd Committee: Ways and Means
Complete to 12-6-20
SUMMARY:
House Bill 4733 would amend the Michigan Vehicle Code to change procedures for setting
certain speed limits on Michigan highways.1
Section 627 of the Michigan Vehicle Code establishes Michigan’s “Basic Speed Law,” which
generally requires that drivers keep to a speed that will allow their vehicle to stop safely under
current road conditions. Section 627 also provides general speed limits for various types of
roads and in the state—gravel roads, for example, or roads that are in a business district or
mobile home park. These constitute a kind of default setting or standard for establishing the
speed limit for any given stretch of road. For a driver, they are the speed limits that apply when
there are no speed limit signs (as long as the Basic Speed Law is obeyed).
Section 628 of the code provides procedures under which the Michigan Department of
Transportation (MDOT) and county and local road authorities can modify those general speed
limits to account for local circumstances. This is the section the bill would amend.
Determining a modified speed limit
Currently, a modified speed limit under section 628 must be determined by an engineering and
safety study and by the eighty-fifth percentile speed of free-flowing traffic under ideal
conditions of a section of highway rounded to the nearest multiple of five miles per hour. (The
eighty-fifth percentile speed is the speed that 85% of the drivers on a given section of roadway
are currently driving at or below.)
The bill would remove the reference to an engineering and safety study and require instead that
the modified speed limit be determined “in accordance with traffic engineering practices that
provide an objective analysis of the characteristics of the highway” as well as by the eighty-
fifth percentile speed. The bill would also require that the speed limit be rounded to a multiple
of five miles an hour that is within five miles an hour of the eighty-fifth percentile speed.
The bill would add that a speed limit could be set below the eighty-fifth percentile speed if an
engineering and safety study demonstrated a situation with hazards to public safety that are not
reflected by the eighty-fifth percentile speed. However—and as under current law—the speed
limit could not be set below the fiftieth percentile speed (that is, the speed that half the drivers
on a given section of roadway are currently driving at or below).
MCL 257.628
1
See https://www.michigan.gov/documents/Establishing_Realistic_Speedlimits_85625_7.pdf
House Fiscal Agency Page 1 of 2
FISCAL IMPACT:
The bill would amend section 628 of the Michigan Vehicle Code, which prescribes procedures
for establishing speed limits on public highways and provides for exceptions to those general
standards. Specifically, as described above, the bill would provide for the establishment of
speed limits lower than the general eighty-fifth percentile standard in specified circumstances.
The bill does not appear to establish new procedures that would materially affect the cost of
traffic and speed studies and thus would have no direct fiscal impact on the state or local units
of government.
POSITIONS:
Representatives of the following entities testified in support of the bill (9-1-20):
• Holland Police Department
• League of Michigan Bicyclists
The following entities indicated support for the bill:
• Michigan Townships Association (12-3-20)
• Michigan Municipal League (12-3-20)
• Detroit Greenways Coalition (12-3-20)
• City of Ann Arbor (9-1-20)
• Michigan Association of Chiefs of Police (9-1-20)
The Department of State Police indicated a neutral position on the bill. (9-1-20)
The following entities indicated opposition to the bill:
• Washtenaw Bicycling and Walking Coalition (9-1-20)
• County Road Association (9-1-20)
Legislative Analyst: E. Best
Fiscal Analyst: William E. Hamilton
■ This analysis was prepared by nonpartisan House Fiscal Agency staff for use by House members in their
deliberations, and does not constitute an official statement of legislative intent.
House Fiscal Agency HB 4733 (H-1) as referred from Transportation Page 2 of 2

Statutes affected:
House Introduced Bill: 257.628