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 set 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.
Roads are grouped by agency in control.
Jump to: MDC, MassHighway,
Turnpike, cities and towns.
|Metropolitan District Commission|
|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|
|Boston||E. of West Roxbury Parkway||35||42||48||9|
|Centre Streeet||Boston||Westchester Road||30||38||43||4|
|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|
|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|
|Fresh Pond Parkway||Cambridge||Fresh Pond Lane||30||36||40||6|
|Longfellow Bridge||Cambridge||Memorial Drive ramp||30||40||47||6|
|Turnpike extension||Boston||Mass. Ave.||55||61||67||20|
|Warren||Little Bemis Road||65||71||77||16|
|Route 1||Newbury||S. of Hanover||55||52||57||80|
|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|
|Concord||Sandy Pond Road||45||55||61||6|
|Acton||W. of 27||55||64||72||11|
|Templeton||Otter River Road||55||65||72||3|
|Route 2A||Lexington||Emerson Gardens Road||35||37||42||34|
|Route 3||Bedford||Old Billerica Road||55||66||73||2|
|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|
|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|
|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|
|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|
|Medford||Exit 33 (NB)||55||66||72||13|
|Medford||Exit 33 (SB)||55||71||77||4|
|Medford||Exit 31 (SB)||55||65||74||10|
|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|
|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|
|Route 126||Bellingham||Fox Run Road||35*||42||45||8|
|Commonwealth Avenue||Brighton||W. of Harvard Street||30*||36||41||16|
|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|
|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|
|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. 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.
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.
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, firstname.lastname@example.org
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