Ever notice that a lot of people seem to be driving faster than the speed limit?

It might surprise you to learn that if speed limits were based on traffic engineering standards, as required by federal law, this would never happen. Most drivers choose safe speeds on their own, so the engineering standard is to set a speed limit near the 85th percentile speed of free flowing traffic. That means the violation rate should be 15% or less. A majority of speeding cars is proof that the speed limit is too low.

This table compares 85th percentile speeds to actual speed limits at a number of locations in the Boston area.

  • “Limit” means the current speed limit. * means the posted limit is not legal.
  • “50th” means the 50th percentile (median) speed.
  • “85th” means the 85th percentile speed.
  • “%” means percent of drivers voluntarily obeying the speed limit (i.e. not following behind a slower car).

Roads are grouped by agency in control.

Massachusetts SPEEDS AND SPEED LIMITS
Metropolitan District Commission
Road City Location Limit 50th 85th %
Charles River Road Watertown E. of Watertown Square 30 39 44 1
Greenough Blvd. Watertown N. of Arsenal Street 40 45 50 17
S. of Arsenal Street 30 38 44 5
Hammond Pond Parkway Newton S. of Beacon Street 30 44 50 0
Brookline S. of Route 9 40 45 50 22
VFW Parkway Boston St. Josephs Cemetary 35 41 45 8
Brookline South Street 35 40 46 20
Boston E. of West Roxbury Parkway 35 42 48 9
Centre Streeet Boston Westchester Road 30 38 43 4
Jamaicaway Boston Parkwood Terrace 25 36 39 0
West Roxbury Parkway Boston Bellevue Hill Road 40 42 46 36
Storrow Drive Boston EB at Clarendon Street 40 52 59 0
WB at Clarendon Street 40 49 57 9
BU Bridge 40 53 59 1
Soldiers Field Road Boston Western Ave. Bridge 40 50 56 4
W. of Eliot Bridge 35 42 49 11
EB E. of Beacon Street 30 42 46 4
WB E. of Beacon Street 35 46 52 3
Nonantum Road Boston W. of N. Beacon Street 40 45 49 19
Memorial Drive Cambridge EB E. of Mass. Ave. 35 42 48 12
WB E. of Mass. Ave. 35 39 42 22
BU Bridge 35 42 47 9
Fresh Pond Parkway Cambridge Fresh Pond Lane 30 36 40 6
Longfellow Bridge Cambridge Memorial Drive ramp 30 40 47 6
Turnpike Authority
Road City Location Limit 50th 85th %
Turnpike extension Boston Mass. Ave. 55 61 67 20
Market Street 55 67 73 4
Newton Walnut Street 55 65 71 5
Woodland Street 55 63 69 11
Turnpike Weston Winter Street 65 69 75 23
Westborough Spring Road 65 71 78 19
Oxford Merriam Road 65 71 77 22
Warren Little Bemis Road 65 71 77 16
Stockbridge Route 102 65 71 77 15
MassHighway
Road City Location Limit 50th 85th %
Route 1 Newbury S. of Hanover 55 52 57 80
Danvers Peabody C.L. 50 50 58 50
Plainville S. of 152 55 49 56 85
Route 2 Belmont Route 60 55 66 71 5
Lexington W. of Pleasant St. 55 67 74 4
Lincoln Page Road 45 55 62 6
Concord Sandy Pond Road 45 55 61 6
Acton W. of 27 55 64 72 11
Lancaster Exit 36 55 65 71 11
Templeton Otter River Road 55 65 72 3
Phillipston Highland Ave. 55 59 63 26
Route 2A Lexington Emerson Gardens Road 35 37 42 34
Lexington Tufts Road 30 38 42 2
Lincoln Bedford Lane 40 44 49 17
Route 3 Bedford Old Billerica Road 55 66 73 2
Weymouth Middle Street 60 64 68 36
Norwell River Street 60 66 72 19
Route 6 Yarmouth West Yarmouth Road 55 65 73 3
Route 7 Sheffield S. of Great Barrington T.L. 55 52 57 83
Wiliamstown S. of Route 2 45 45 50 53
Route 8 Sandisfield S. of 57 55 57 63 41
Route 9 Newton Parker Street 50 50 55 50
Wellesley Emerson Road 50 54 60 29
Williamsburg Post Office 25 33 37 3
Williamsburg E. of South Street 25 34 39 4
Windsor E. of 8A 55 58 63 35
Route 10 Bernardston E. of I-91 55 53 58 61
Route 20 Watertown Emerson Road 35 37 41 38
Waltham Summit Avenue 35 37 42 32
Weston Crescent Street 40 41 44 49
Weston Linwood Avenue 45 44 47 72
Brimfield 2.8 mi. W. of Sturbridge 55 57 64 40
Lenox S of 7A 55 55 62 51
Route 24 Berkley Bryant Street 65 71 77 20
Route 28 Milton Ridgewood Street 45 50 56 24
Quincy Skyline Trail 50 47 53 71
Route 88 Westport S. of Old County Rd. 55 58 67 32
I-91 West Springfield N. of Route 5 65 67 73 46
Northampton S. of Route 5&10 65 67 73 46
I-93 Milton Exit 3 55 68 76 4
Milton Pleasant Street 55 61 67 24
Medford Exit 33 (NB) 55 66 72 13
Medford Exit 33 (SB) 55 71 77 4
Wilmington N. of Route 62 65 69 77 31
I-95 Boxford near Route 133 65 72 78 18
Route 112 Goshen S. of Ashfield T.L. 55 58 64 37
Route 125 Andover S. of 28 50 54 59 21
Route 128 Gloucester S. of Concord St. 55 62 69 24
Waltham Route 117 55 67 73 6
Needham Kendrick Street 55 66 71 5
Needham N. of Great Plain Ave. 55 65 73 7
Route 135 Wellesley Bacon Street 45 48 53 31
Route 138 Milton Canton T.L. 40 41 46 46
Route 146 Millbury Route 122A 50 61 68 5
I-195 Mattapoisett W. of North St. 65 68 76 36
Fall River Route 24 55 62 69 22
I-290 Worcester East Central St. 50 57 64 14
I-495 Bolton N. of 62 65 68 74 36
Amesbury S. of I-95 65 69 75 26
Cities and towns
Road City Location Limit 50th 85th %
Route 126 Bellingham Fox Run Road 35* 42 45 8
Commonwealth Avenue Brighton W. of Harvard Street 30* 36 41 16
Evergreen Cemetery 30* 37 42 9
Jewish War Veterans Drive Dorchester Franklin Park 25* 37 41 2
Washington Street West Roxbury Cowing Street 25* 40 47 0
Middlesex Turnpike Burlington Terrace Hall Ave. 35 41 46 14
Dover Road Dover Main St. 30* 39 43 2
Route 109 Millis Dover Road 40* 45 50 17
Spring Street Lexington Underwood Ave. 30* 37 41 3
Greendale Avenue Needham Highgate Street 40 42 46 35
Auburn Street Newton W. of Washington Street 25 34 38 1
Chestnut Street Newton Kodaya Road 25* 34 38 4
Lexington Street Newton N. of Auburndale Ave. 30 36 40 8
Commonwealth Avenue Newton E. of 128 35 38 42 14
E. of 16 35 41 45 9
E. of Walnut 35 36 40 48
Washington Street Newton E. of 30 35 37 41 27
W. of 30 35 36 41 39
Route 181 Palmer South High Street 40 40 44 51
Route 16 Watertown Derby Road 30* 32 37 28
Walnut Street 30* 34 38 20
Route 30 Weston Ware Street 45 42 46 81

Speeds on the Turnpike, MDC parkways, city and town roads, and some state highways in the Boston area were measured with a LIDAR speed measuring device in 2000 and 2001 and in 2005. Speeds for other state highways were measured by MassHighway loop sensors in 1999 and are totals for a complete day instead of just free-flowing traffic. Traffic speeds are usually very similar in both directions. When speeds in both directions are available and differ significantly, both are listed separately. Otherwise the average is listed.

What does this mean?

The national standard is to round the 85th percentile up to the next multiple of 5 MPH to determine a speed limit. None of the roads measured meets that standard. Only a few are within 5 MPH. All but one of these are minor state highways where engineers have been permitted to have some influence in the process of setting speed limits.

The MDC doesn’t do engineering studies, and it shows. Typical speed limits are 15 MPH too low. Both Hammond Pond Parkway and Storrow Drive have speed limits 20 MPH too low.

Speed limits on major highways are set by politicians. Compliance is around 5% in 55 MPH zones (which were mostly posted 60 until 1974) and up to 25% in 65 MPH zones. Based on these measurements, speed limits should be increased from 55 and 65 to 70, 75, and 80.

*The speed limit in Franklin Park, Boston is illegal because it has not been approved by the state. The Mayor, who was almost hit by a car, insists on strict enforcement of the illegal speed limit. The limit should be 40, not 25. Commonwealth Avenue is also illegally posted.

*Middlesex Turnpike in Burlington was rebuilt a few years ago, widened to four lanes plus left turn lanes at intersections. The 35 MPH speed limit for the old road has been posted on the new road.

*Dover Road, Dover is illegally posted 30. The town Police Chief has admitted the signs are illegal:

Chief's Letter

*Spring Street, Lexington is illegally posted 30. The authorized limit is 35; 31% of drivers obey that limit.

*Route 16, Watertown, is illegally posted 30. No speed limit is authorized; the proper speed limit would be 35.

*Gardner St in Hingham is illegally posted: Channel 4 did a story here

Many other speed limits were only 5 MPH too low when they were set, but now they are much too low. Cities and towns don’t like to change speed limits, and some limits have remained unchanged since the early 1950s!

Feedback to John Carr, jfc@motorists.org