Tech Note #66 – Massachusetts Speed Laws

Speed Limits & Speed Limit SettingBackground
The National Highway Traffic Safety Administration (NHTSA) defines speeding as “travelling in excess of the posted speed limit” or “driving too fast for conditions.”   Nationally, speed-related crashes account for 30 percent of all fatal crashes, resulting in over 10,000 fatalities annually and a societal cost exceeding $40 billion.  The numbers in Massachusetts are similar where 30 percent of the 349 fatalities in 2012 were speed-related.  In Massachusetts, 56 percent of speed-related fatalities occurred on roadways with a posted speed limit of 35 mph or less, and 78 percent of speed-related fatalities occurred on a roadway with a posted speed limit of 45 mph or less. From an engineering standpoint properly posted speed limits represent the front lines of speed management.  This Tech Note provides basic information regarding speed limits and guidance on proper speed limit setting and sign posting.

Speed Laws in Massachusetts
Within the Massachusetts General Laws (MGL) there are two sections that deal specifically with speed limits.
MGL Chapter 90, Section 18  allows for the posting of numerical limits on the typical speed limit sign.  This law also indicates that the limit  must  be  based  on  engineering  study  and  needs approval via a Special Speed Regulation approved by the Registry of  Motor  Vehicles (RMV)  and  MassDOT. Please note that  all regulatory speed limit signs not posted under this procedure are in violation of the law and are not legally enforceable.*
MGL Chapter 90, Section 17 applies to unposted roadways and specifically states that it shall be prima facie evidence of a rate of speed greater than is reasonable and proper as aforesaid (1) if a motor vehicle is operated on a divided highway outside a thickly settled or business district at a rate of speed exceeding fifty miles per hour for a distance of a quarter of a mile, or (2) on any other way outside a thickly settled or business district at a rate of speed exceeding forty miles per hour for a distance of a quarter of a mile, or (3) inside a thickly settled or business district at a rate of speed exceeding thirty miles per hour for a distance of one-eighth of a mile, or (4) within a school zone which may be established by a city or town as provided in section two of chapter eighty-five at a rate of speed exceeding twenty miles per hour.
*Please note there are special speed law provisions in the MGL for the Massachusetts Turnpike and Department of Conservation and Recreation (DCR) [formerly the Metropolitan District Commission (MDC)] Roads.

Setting Speed Limits
Municipalities should contact MassDOT to request speed limit posting on state-owned roadways. It is the responsibility of the municipality to follow the procedures for locally-owned roadways, which require approval by both MassDOT and the RMV. When considering the establishment of speed limits it is imperative that you review the following two sources which will provide specific guidance on speed zoning: (1)  Procedures for Speed Zoning on State and Municipal Roads, and (2) The Manual on Uniform Traffic Control Devices (MUTCD Section 2B.13).
The establishment of a speed limit is required to be based upon an engineering study, and any resulting posting must be in increments of 5 mph. One major basis for the setting of speed limits is that most motorists are able to select a reasonable and safe speed. Using the 85th Percentile speed as a baseline, the proposed speed limit may be adjusted based upon additional factors, including, road characteristics (e.g., shoulder condition, grade, alignment, and sight distance), the pace speed, roadside development and environment, parking practices and pedestrian activity, and reported crash experience.
Engineering Study
An engineering study from the municipality must contain both the collected data and analysis of this data. Data collection includes:
1.   Preliminary study of conditions;
2.   Speed calculations of curves
(MassDOT’s responsibility);
3.   Speed observations;
4.   Studies of crash             distributions; and
5.   Trial runs over the         location.

Speed  observations  are  determined from a spot speed study and are representative  of  the  motorists “opinion” regarding the speed limit. Speeds from 100 free flow vehicles (drivers choosing their own speed, i.e., not  in  queue)  should  be  captured  in each direction.  Data analysis includes:
1.   Safe speed range;
2.   Selecting speed limits/lengths of zone;
3.   Advisory speeds; and
4.   Rechecks with trial runs.

Advisory Speeds
Special consideration should always be given to the safe speeds for curves, hills and other locations located within that portion of the section. If the safe speed determined by a Ball-Bank Indicator through a particular curved section of a roadway differs from the preceding speed zone by 10 miles per hour or less, and the curved section of roadway is less than 0.20 miles, or if engineering judgment determines that it is appropriate, a warning sign used in conjunction with an advisory speed plate indicating the safe speed can be used in lieu of establishing a separate speed zone for an isolated condition.
Section 2C-08 of the 2009 Manual on Uniform Traffic Control Devices (M.U.T.C.D.) states: Section 2C.08 Advisory Speed Plaque (W13-1P)
The Advisory Speed (W13-1P) plaque (see Figure 2C-1) may be used to supplement any warning sign to indicate the advisory speed for a condition.
The use of the Advisory Speed plaque for horizontal curves shall be in accordance with the information shown in Table 2C-5. The Advisory Speed plaque shall also be used where an engineering study indicates a need to advise road users of the advisory speed for other roadway conditions.
If used, the Advisory Speed plaque shall carry the message XX MPH. The speed displayed shall be a multiple of 5 mph.
Except in emergencies or when the condition is temporary, an Advisory Speed plaque shall not be installed until the advisory speed has been determined by an engineering study.
The Advisory Speed plaque shall only be used to supplement a warning sign and shall not be installed as a separate sign installation.

The advisory speed shall be determined by an engineering study that follows established engineering practices.
Unlike regulatory speed signs, advisory speed signs can be erected by municipalities without any further approval provided they comply with the M.U.T.C.D. Also, advisory speeds are not enforceable, since their intent is to advise motorists of an appropriate speed through a particular condition, not regulate it.

School Zones
The 20 mph speed limit on roads near schools can be posted in various
ways. When posting signs, it is important to consider providing motorists with information as to the beginning and end of the school zone as well as when the 20 mph speed limit is in effect. The signs stating such limits may be accompanied by flashing yellow lights or posted for certain hours of the day and days of the week.
Section 7B.15 of the 2009 Manual on Uniform Traffic Control Devices (M.U.T.C.D.) states: Section 7B.15 School Speed Limit Assembly (S4-1P, S4-2P, S4-3P, S4-4P, S4-6P, S5-1) and END SCHOOL SPEED LIMIT Sign (S5-3)
The School Speed Limit assembly shall be either a fixed-message sign assembly or a changeable message sign.
The fixed-message School Speed Limit assembly shall consist of a top plaque (S4-3P) with the legend SCHOOL, a Speed Limit (R2-1) sign, and a bottom plaque (S4-1P, S4-2P, S4-4P, or S4-6P) indicating the specific periods of the day and/or days of the week that the special school speed limit is in effect (see Figure 7B-1).
Changeable message signs (see Chapter 2L and Section 6F.60) may be used to inform drivers of the school speed limit. If the sign is internally illuminated, it may have a white legend on a black background. Changeable message signs with flashing beacons may be used for situations where greater emphasis of the special school speed limit is needed.
Even though it might not always be practical because of special features to make changeable message signs conform in all respects to the standards in this Manual for fixed-message signs, during the periods that the school speed limit is in effect, their basic shape, message, legend layout, and colors should comply with the standards for fixed-message signs.
A confirmation light or device to indicate that the speed limit message is in operation should be considered for inclusion on the back of the changeable message sign.

Mass Interchange, Spring 2014


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