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FHWA Home / Safety / Speed Management / Engineering Countermeasures for Reducing Speeds

Engineering Speed Management Countermeasures

A Desktop Reference of Potential Effectiveness in Reducing Speed

July 2014

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This chart summarizes studies about engineering countermeasures used to manage speeds. Studies where an increase in speed were reported are also shown since this information is also relevant in selection of countermeasures. For the most current information on Crash Modification Factors (CMF), please go to the CMF Clearinghouse at: http://www.cmfclearinghouse.org.

Countermeasure Safety Focus Area Roadway  Reference Sites Speed limit (mph) Volume (vpd) Mean Speed (mph) 85th %tile Speed (mph) Period Location Notes
Before After Before After Change Before After Change
Vertical Deflections Within the Roadway
Speed Hump — rounded, raised area placed across the roadway, typically 12 to 14 feet long  pedestrian urban local  1 (1999) 178 48 to 11544 46 to 110443 35 27 -8 various
pedestrian urban local  2 (2005) 7 400 to 4362 401 to 3384 32 26 -6 VA  
pedestrian urban local  3 (2000) 4 475 to 1506 433 to 1343 36 31 -5 WA
pedestrian urban local 4 (2005) 1 25 1300 22 23 1 37 29 -8 1-mon FL
pedestrian rural/urban local 5 (2002) 3 25 218 to 746 24 18 -6 28 22 -6 1-mon IA
pedestrian urban 1 (1999) 4 36 29 -7 with speed table
pedestrian urban 1 (1999) 2 2456 to 3685 2593 to 2931 38 25 -13 with choker
Speed Cushion — raised area typically 6 to 7 feet wide that allows most emergency vehicles to straddle the hump pedestrian urban 1 (1999) 1 3323 2321 35 28 -7 various
pedestrian 2 (2005) 2 1042 to 1556 693 to 1563 31 to 37 26 to 30 -5 to -7 VA
Speed Table — a long speed hump typically 22 feet in length with a flat section in the middle and ramps on the ends pedestrian urban 1 (1999) 72 198 to 14500 242 to 14400 37 31 -6 various
pedestrian urban residential 6 (2003) 19 198 to 2102 364 to 2061 38 29 -9 GA
pedestrian rural community 2-lane 7 (2007) 1 1200 27 24 -3 33 29 -4 1-mon IA
pedestrian rural community local 5 (2002) 3 25 218 to 746 24 18 -6 28 22 -6 1-mon IA removable speed table
pedestrian urban 1 (1999) 2 6500 to 8440 6400 to 6780 37 29 -8 with center island 
pedestrian urban residential 8 (2001) 1 30 1600 34 23 -11 38 27 -11 within 12-mon MN raised crosswalk
Raised Intersection — a raised plateau, with ramps on all approaches, where roads intersect  pedestrian urban 1 (1999) 2 37 38 1 various
pedestrian urban local 9 (2004) 1 30 30 0 12-mon NY
Horizontal Deflections/Roadway Narrowing
Choker/Bulb-out— mid-block curb extensions that narrow road by extending the sidewalk or widening the planting strip  pedestrian urban 1 (1999) 4 750 to 6150 331 to 5040 34 30 -4 various
pedestrian urban residential 10 (1997) 6 30 29 -1
pedestrian urban residential 8 (2001) 1 950 to 1050 34 31 -4 38 34 -4 within 12-mon MN choker with crosswalk
pedestrian urban residential 8 (2001) 1 950 to 1050 33 31 -2 37 34 -3 within 12-mon MN choker + "SLOW" + landscaping
pedestrian rural community 2-lane 11 (2010) 39 39 0 simulator curb + gutter bulb-outs
Neck Down — intersection curb extensions that narrow a road by extending the width of a sidewalk   pedestrian urban 1 (1999) 3 2800 to 8110 4660 to 5660 29 30 1 various
pedestrian urban local street 9 (2004) 2 23 25 2 27 31 y 12-mon NY
Chicanes— curb extensions that alternate from one side of the street to the other forming s-shaped curves, also includes lateral shifts which shift traffic to one side of the road for an extended distance and then back  pedestrian urban 10 (1997) 2 1380 to 3200 790 to 2400 33 27 -6 various
pedestrian urban residential 3 (2000) 4 1380 to 1965  790 to 1993 31 22 -9 at least 4 years WA
pedestrian urban arterial (school zone) 12 (1998) 1 8000 31 28 -3 Canada
pedestrian rural community 2-lane 11 (2010) 39 30 -9 simulator
pedestrian rural community 2-lane  11 (2010) 39 33 -6 simulator painted chicane
Center Island— raised or painted island along the centerline that narrows travel lanes  pedestrian urban 1 (1999) various
pedestrian urban 1 (1999) 2 6500 to 8440 6400 to 6780 37 29 -8
pedestrian urban y 9 (2004) 1 30 28 -2 36 33 -3 12-mon NY
pedestrian rural 13 (2002) 2 44 38 -6 1-mon MN
pedestrian rural within community (2-lane) 13 (2002) 1 30 900 34 29 -5 44 38 -6 2-wks MN
pedestrian rural within community (2-lane) 13 (2002) 1 30 900 35 31 -4 44 38 -6 6-wks MN
pedestrian rural community entrance (2-lane) 7 (2007) 2 25 2669 31 29 -1 36 35 -1 1-mon IA combined + tubular channelizers
pedestrian rural community entrance (2-lane) 14 (2008) 35 41 43 2 51 50 -1 simulator median
Center Island — raised or painted island along the centerline that narrows travel lanes  pedestrian rural community entrance (2-lane) 14 (2008) 35 41 40 -1 52 46 -6 simulator median + gateway
pedestrian rural community entrance (2-lane) 14 (2008) 35 41 41 0 52 50 -2 simulator median in series
pedestrian rural community entrance (2-lane) 14 (2008) 35 41 40 -1 51 46 -5 simulator median in series with crosswalk
pedestrian rural community entrance (2-lane) 15 (2013) 3 25 593 to 1448 28 27 1 35 34 -1 1-mon IA temporary curbing
pedestrian rural community entrance (2-lane) 15 (2013) 3 25 593 to 1448 29 27 -2 35 33 -2 12-mon IA temporary curbing
pedestrian rural community entrance (2-lane) 16 (1999) 5 38 29 -9 44 33 -11 Austria braking islands
roadway departure rural 2-lane 17 (2008) 8 50 to 55 -4 -5 Austria painted island + edge line
Reduce Lane Width with Markings — narrowing of the lanes using pavement markings, median, etc.  pedestrian rural community 2-lane 7 (2007) 2 30 1680 28 29 1 34 35 1 1-mon IA narrowing with pavement marking 
pedestrian rural community 2-lane 7 (2007) 2 30 1680 28 29 1 34 35 1 12-mon IA narrowing with pavement marking 
pedestrian urban residential 18 (1984) 2 0 1-wk FL narrowing using edgeline + centerline
intersection rural intersection (2-lane) 19 (2008) 9 50 to 55 -4 -5 3-mon PA, KY, MO, FL edgeline + centerline
roadway departure urban high speed intersection 4-lane 20 (2008) -4 2.7 ft. lane width reduction
roadway departure urban freeway exit 21 (2000) 31 30 -1 1-mon VA narrowing using herringbone markings
roadway departure rural day 2-lane 22 (2005) 3 57 58 1 1-mon TX edgeline + centerline
roadway departure rural night 2-lane 22 (2005) 3 1 1-mon TX edgeline (existing centerline)
Road Diet — reducing the number of lanes by reallocating roadway space for other uses (e.g. bike lanes, center turn lanes, medians, parking, shoulder  lanes, etc. pedestrian urban 4-lane undivided 23 (2001) 1 -4 CA 4- to 3-lane
pedestrian urban 4-lane undivided 23 (2001) 1 35 32 -3 IA 4- to 3-lane
pedestrian urban 4-lane undivided 23 (2001) 1 -1 IA 4- to 3-lane
pedestrian urban minor arterial 8 (2001) 1 35 5400 to 9100 45 43 -2 51 49 -2 MN 4- to 3-lane
Surface Treatments and Markings
Transverse Rumble Strips — raised or grooved patterns installed on the roadway travel lane or shoulder pavements perpendicular to the direction of travel   pedestrian rural  high-speed intersection 20 (2008) 3 70 -1 5-mon
pedestrian rural    intersection 24 (2003) 11 55 54 -1 1-mon TX
roadway departure rural 2-lane 25 (2005) 3 46 46 0 49 52 3 1-wk KY cars
work zone rural work zone (2-lane) 26 (2000) 2 1250 to 1850 -2 1-day TX cars
work zone rural work zone (2-lane) 26 (2000) 2 1250 to 1850 -2 1-day TX trucks
Transverse Bars — lines placed across the lane perpendicular to direction of travel pedestrian rural community entrance (2-lane) 15 (2013) 3 843 to 1947 38 37 -1 44 44 0 1-mon IA
pedestrian rural community entrance (2-lane) 15 (2013) 3 843 to 1947 37 38 1 44 43 -1 12-mon IA
work zone rural work zone (4-lane divided) 39 (2003) 1 -2 Canada
work zone rural work zone    40 (2001) 1 70 18000 64 63 -1 68 67 -1 KS
Converging Chevrons — on-pavement chevrons  roadway departure rural freeway to freeway ramp 36 (2003) 39010 64 49 -15 70 53 -17 20-mon WI
roadway departure rural freeway to freeway ramp 37 (2008) 30 adv. 18000 47 47 0 53 52 -1 1-mon TX
roadway departure rural freeway to freeway ramp 37 (2008) 30 adv. 18000 48 48 0 53 53 0 6-mon TX
roadway departure rural S-curve  (2-lane) 38 (2006) 1 35/15 adv. 37 33 -4 15-mon OH
pedestrian rural intersection 8 (2001) 1 30 4000 36 32 -4 41 35 -6 1-wk MN
pedestrian rural intersection 8 (2001) 1 30 4000 36 34 -2 41 39 -2 2-yr MN
pedestrian rural intersection 8 (2001) 1 30 4000 36 31 -5 41 35 -5 4-yr MN
pedestrian rural community entrance 7 (2007) 2 25 2200 to 2420 30 29 -1 36 35 -1 1-mon IA
pedestrian rural community entrance 7 (2007) 2 25 2200 to 2420 30 29 -1 36 33 -3 12-mon IA
roadway departure rural freeway to freeway ramp 35 (2010) 18000 to 18600 31 29 -2 35 33 -2 1-mon GA
roadway departure rural freeway to freeway ramp 35 (2010) 18000 to 18600 31 30 -1 35 34 -1 9-mon GA converging chevrons
Optical Speed Bars – transverse stripes on travel lane (sometimes spaced progressively closer to create the illusion of traveling faster) pedestrian rural intersection 20 (2008) 4 -1 -1
pedestrian rural community entrance 7 (2007) 3 25 to 30 886 to 1870 39 38 -1 47 46 -1 1-mon IA
pedestrian rural community entrance 7 (2007) 2 25 to 30 234 to 662 263 to 646 39 34 -5 47 42 -5 1-mon IA with  DSFS —"YOUR SPEED XX" 
Optical Speed Bars – transverse stripes on travel lane (sometimes spaced progressively closer to create the illusion of traveling faster) pedestrian rural intersection 27 (2010) 1 4,450 53 51 -2 62 60 -2 6-mon New Zealand herringbone pattern
pedestrian rural community entrance 28 (2011) 1 2800 37 29 -8 Italy with dragon's teeth 
intersection rural intersection (2-lane) 29 (2013) 1 37 42 31 -11 48 3 -13 12-mon Spain with RPM + reflectors to guardrail
intersection rural intersection 30 (2000) 62 -6 simulator Australia full lane width 
intersection rural intersection 30 (2000) 62 -4 simulator Australia optical speed bar
roadway departure rural horizontal curves 25 (2005) 3 46 46 0 49 49 0 1-wk KY transverse bars
roadway departure rural horizontal curves 25 (2005) 3 46 45 -1 49 51 2 1-yr KY transverse bars
roadway departure rural 4- lane undivided 31 (2007) 2 45 12000 55 52 -3 1-wk VA transverse bars
roadway departure rural 4- lane undivided 31 (2007) 2 45 12000 56 49 -7 3-mon VA transverse bars
roadway departure rural curve       (2-lane) 32 (2007) 2 45 -65/40 adv. 48 49 1 52 56 4 4-mon NY, MI, TX optical speed bar
roadway departure rural curve         (2-lane) 31 (2007) 5215 46 44 -2 1-wk VA optical speed bar
roadway departure rural curve       (2-lane) 31 (2007) 5215 46 45 -1 3-mon VA optical speed bar
roadway departure rural 2-lane    33 (2009) 55 day 45 night 64 62 -2 71 69 -2 1-wk AZ optical speed bar
roadway departure rural 2-lane    33 (2009) 55 day/ 45 night 64 59 -4 71 68 -3 3-mon AZ optical speed bar
roadway departure rural curve (freeway) 34 (2008) 50 57 54 -3 60 59 -1 1-wk WI optical speed bar
roadway departure rural freeway exit ramp 32 (2007) 1 65/30 adv. 38 34 -4 44 39 -5 4-mon NY, MI, TX optical speed bar
roadway departure rural 2-lane 27 (2010) 1 2500 51 50 -1 60 59 -1 2-wk New Zealand herringbone
roadway departure rural 2-lane 27 (2010) 1 2500 51 48 -3 60 60 0 6-mon New Zealand herringbone
roadway departure rural freeway ramp 21 (2000) 4 2-wk NY, VA herringbone markings
pedestrian rural intersection 27 (2010) 1 4,450 53 52 -1 61 61 0 2-wks Herringbone
"SLOW" Legend on Pavement pedestrian urban residential 8 (2001) 1 30 950 28 29 0 32 33 1 MN
roadway departure urban curve (2-lane) day 41 (1998) 1 35/15 adv 5000 34 33 -1 2-wk VA with curve symbol
roadway departure urban curve (2-lane) night 41 (1998) 1 35/15 adv 5000 35 32 -3 2-wk VA with curve symbol
roadway departure rural  curve    15 (2012) 2 55/none to 35 mph 780 to 1880 49 48 -1 54 53 -1 1-mon IA with curve symbol+ bars
roadway departure rural  curve  15 (2012) 2 55/none to 35 mph 780 to 1880 49 48 -1 54 53 -1 12-mon IA with curve symbol + bars
Speed Limit XX Pavement Legend pedestrian rural within community 7 (2007) 1 25 2200 30 30 0 35 34 -1 1-mon IA
pedestrian rural within community 7 (2007) 1 25 2200 30 29 -1 35 33 -2 12-mon IA
pedestrian rural within community 7 (2007) 1 25 2420 1-mon IA with lane narrowing
pedestrian rural within community 7 (2007) 1 25 2420 28 29 1 32 33 1 12-mon IA with lane narrowing
pedestrian rural community entrance 7 (2007);15 (2013) 5 25 to 35 1009 to 2850 37 35 -2 42 40 -3 1-mon IA with red colored pavement 
pedestrian rural community entrance 7 (2007);15 (2013) 2 25 to 35 1009 to 2850 40 39 -1 46 45 -1 12-mon IA with red colored pavement 
pedestrian rural community entrance 15 (2013) 3 25 to 35 1009 to 3070 35 34 -1 40 39 -1 1-mon IA colored pavement + dragon's teeth
"50 MPH" + Curve Symbol roadway departure urban curve (divided 4-lane highway) 42 2005) 1 67 60 -7 1-mon TX
"CURVE AHEAD" Pavement Legend roadway departure rural curve    42 (2005) 1 990 56 61 5 3-mon TX
"CURVE 55 MPH" Pavement Legend roadway departure rural curve 42 (2005) 1 1160 60 59 -1 3-mon TX
Center Island Using Tubular Channelizers pedestrian rural community community entrance (2-lane) 7 (2007) 2 25 2669 30 29 -1 36 35 -1 1-mon IA
Post Mounted Delineators — reflective buttons place on post at edge of road roadway departure rural curve (2-lane) 25 (2005) 3 46 46 0 49 50 1 1-wk KY
roadway departure rural curve (2-lane) 11 (2010) 43 35 -8 simulator one side of curve
roadway departure rural curve (2-lane) 11 (2010) 43 34 -9 simulator both sides of curve
Streaming PMD roadway departure rural curve (2-lane) 11 (2010) 43 24 -19 simulator
Chevrons with Reflective post roadway departure rural curve (2-lane) 46 (2010) 2 56 54 -2 65 63 -2 1-mon TX
Reflective Post Added To Existing Chevrons roadway departure rural curve (2-lane) 47 (2012) 4 830 to 2280 50 50 0 56 55 -1 1-mon IA
roadway departure rural curve (2-lane) 47 (2012) 1 1710 54 53 -1 59 57 -2 12-mon IA
Layered Landscaping – roadside plantings used to create vertical friction pedestrian rural  community entrance (2-lane) 14 (2008) 35 43 44 1 54 53 -1 simulator at treatment
pedestrian rural  community entrance (2-lane) 14 (2008) 35 42 40 -2 51 45 -6 simulator 300 ft. downstream of treatment
Landscaped Median roadway departure urban collector 48 (2000) 1 11400 10900 37 33 -4 43 37 -6 CO with curbside islands
Dynamic Signing
Speed Activated Speed Limit Sign – a blank out sign that displays "SPEED LIMIT XX" for vehicles exceeding threshold speed roadway departure urban collector   55 (2013) 1 30 33 27 -6 36 30 -6 2-mon CO with striping between travel/parking lanes + signing
roadway departure urban collector   55 (2013) 2 30 39 34 -5 1-yr CO with physical narrowing + pedestrian refuge
roadway departure urban collector   55 (2013) 3 30 37 33 -4 1-yr CO
roadway departure urban collector   55 (2013) 1 30 37 32 -5 3-yr CO
Speed Limit Sign with LED pedestrian rural community entrance 15 (2013) 2 25 980 to 2240 33 30 -3 42 28 -4 1-mon IA
pedestrian rural community entrance 15 (2013) 2 25 980 to 2240 33 30 -3 42 38 -4 12-mon IA
Speed Feedback Sign - displays the speed of drivers traveling over the  threshold speed with the message "YOUR SPEED XX  pedestrian urban school zone 50 (2005) 3 35 to 45 49 44 -5 55 49 -6 1-wk TX
pedestrian urban school zone 50 (2005) 3 35 to 45 49 42 -7 54 51 -3 4-mon TX
pedestrian rural community entrance 7 (2007); 15 (2013) 1 25 295 367 38 37 -1 46 45 -1 1-mon IA
pedestrian rural community entrance 7 (2007); 15 (2013) 1 25 295 318 38 37 0 46 45 -1 12-mon IA
pedestrian rural community entrance 51 (2006) 4 30 to 45 46 41 -5 51 46 -5 1-mon MN
pedestrian rural community entrance 51 (2006) 4 30 to 45 47 40 -7 51 46 -5 12-mon MN
pedestrian rural community entrance 52 (2009) 12 25 to 40 42 36 -6 1-wk PA
intersection urban signalized intersection 50 (2005) 2 45 to 55 51 47 -4 57 54 -4 1-wk TX
intersection urban signalized intersection 50 (2005) 2 45 to 55 51 49 -2 57 55 -2 4-mon TX
roadway departure urban collector    (2-lane) 53 (2004) 4 25 2700 to 4900 29 28 -1 34 32 -5 1-mon WA
roadway departure urban collector (2-lane) 53 (2004) 4 25 2700 to 4900 28 27 -1 33 28 -5 2-yr WA
roadway departure urban collector/ minor arterial 54 (2009) 16 25 -2 1-yr WA
roadway departure urban collector/ minor arterial 54 (2009) 16 25 -3 5 to 8-yr WA
roadway departure urban collector/ minor arterial 54 (2009) 16 30 to 35 -4 1-yr WA
roadway departure urban collector/ minor arterial 54 (2009) 16 30 to 35 -6 5 to 8-yr WA
roadway departure urban 2-lane 54 (2009) 9 25 to 35 40 36 -4 1-mon WA
roadway departure urban 2-lane 54 (2009) 4 25 to 35 37 33 -4 12-mon WA
roadway departure urban 2-lane 54 (2009) 9 25 to 35 39 35 -4 2 to 3-yr WA
roadway departure urban 2-lane 54 (2009) 11 25 to 35 38 33 -5 4+ yr. WA
roadway departure urban curve (2-lane) 54 (2009) 1 30 41 38 -3 1-mon WA
roadway departure urban curve (2-lane) 54 (2009) 2 30 to 35 42 38 -4 2 to 3-yr WA
roadway departure urban curve (2-lane) 54 (2009) 1 30 41 35 -6 4+ yr. WA
roadway departure rural interstate (curve) 56 (2006) 2 45 adv. 16750 56 53 -3 2 to 4-mon OR passenger cars
roadway departure rural interstate (curve) 56 (2006) 2 45 adv. 16750 51 49 -2 2 to 4-mon OR trucks
roadway departure rural curve (2-lane) 57 (2013) 11 50 to 65/30 to 50 adv. -2 -3 1-mon AZ, FL, IA, OH, OR, TX, WA
roadway departure rural curve (2-lane) 57 (2013) 11 50 to 65/30 to 50 adv. -3 -3 12-mon AZ, FL, IA, OH, OR, TX, WA
roadway departure rural curve (2-lane) 57 (2013) 11 50 to 65/30 to 50 adv. -2 -2 2-yr AZ, FL, IA, OH, OR, TX, WA
roadway departure rural curve (2-lane) 50 (2005) 2 55/20 adv. 36 33 -3 42 39 -3 1-wk TX
roadway departure rural curve (2-lane) 50 (2005) 2 55/20 adv. 36 35 -1 42 40 -2 4-mon TX
roadway departure rural curve (2-lane) 58 (2012) 3 455 to 710 54 51 -3 61 57 -4 1-mon MN passenger cars
work zone rural interstate 62 (2011) 3 55 28000 61 57 -4 66 61 -5 1-wk NE passenger cars
work zone rural interstate 62 (2011) 3 55 28000 58 55 -3 62 59 -3 1-wk NE trucks
work zone rural interstate 62 (2011) 3 55 28000 61 56 -5 66 60 -6 5-wk NE passenger cars
work zone rural interstate 62 (2011) 3 55 28000 58 56 -3 62 59 -3 5-wk NE trucks
work zone rural arterial 63 (2006) 1 66 63 -3 TX
Speed Feedback Sign with Action Message – "YOUR SPEED XX" + "SLOW DOWN" roadway departure urban 2-lane 54 (2009) 9 25 34 32 -2 1 to 6-mon WA
roadway departure urban 2-lane 54 (2009) 3 25 33 -31 -2 12-mon WA
roadway departure urban 2-lane 54 (2009) 5 25 33 31 -2 2 to 3-yr WA
roadway departure urban curve (2-lane) 54 (2009) 1 25 36 31 -5 1 to 6-mon WA
roadway departure urban curve (2-lane) 54 (2009) 1 25 36 31 -5 4+ yr. WA
intersection rural signalized intersection 20 (2008) 3 50 to 55 -2 -1 WA, TX at sign
work zone rural interstate 63 (2006) 1 65 63 -2 TX
pedestrian rural community entrance 7 (2007) 1 25 2870 31 26 -5 59 52 -7 3-mon IA SLOW DOWN 25
Speed Feedback Sign plus New Curve Advisory Speed Sign roadway departure rural curve (2-lane) 58 (2012) 3 455 to 710 54 50 -4 61 57 -4 12-mon MN PC
roadway departure rural curve (2-lane) 58 (2012) 3 455 to 710 53 50 -3 53 50 -3 1-mon MN center of curve, 
roadway departure rural curve (2-lane) 58 (2012) 3 455 to 710 53 50 -3 53 49 -4 12-mon MN center of curve
"YOUR SPEED XX" pedestrian rural community entrance 7 (2007); 15 (2013) 2 25 to 30 234 to 662 263 to 646 39 34 -5 47 42 -5 1-mon IA with optical speed bars
"SLOW" pedestrian rural recreational area 13 (2002) 1 35 36 36 0 43 44 1 1-mon MN
Speed Activated Curve Warning Sign and "SLOW DOWN" Action Message roadway departure rural curve (2-lane) 59 (2002) 3 30 to 50 39 35 -4 United Kingdom
roadway departure rural curve (2-lane) 57 (2013) 11 50 to 70/35 to 50 adv. -2 -2 1-mon AZ, FL, IA, OH, OR, TX, WA
roadway departure rural curve (2-lane) 57 (2013) 11 50 to 70/35 to 50 adv. -3 -2 12-mon AZ, FL, IA, OH, OR, TX, WA
roadway departure rural curve (2-lane) 57 (2013) 11 50 to 70/35 to 50 adv. -2 -2 2-yr AZ, FL, IA, OH, OR, TX, WA
"TOO FAST FOR CURVE" roadway departure rural curve (interstate) 60 (2003) 1 50 -3 WI trucks
"50 MPH CURVES" + "YOUR SPEED XX" roadway departure rural interstate 61 (2000) 5 55 to 65/50 to 60 adv. 64 63 -1 CA passenger cars
"50 MPH CURVES" + "YOUR SPEED XX" roadway departure rural interstate 61 (2000) 5 55 to 65/50 to 60 adv. 58 56 -2 CA trucks
Flashing Beacon work zone rural 2-lane 64 (2007) 3 45 -3 -3 SC
work zone rural multi-lane 64 (2007) 1 45 -3 -3 SC
work zone rural interstate 64 (2007) 1 45 -6 -5 SC
Variable Speed Limit roadway departure rural freeway 65 (2005) 2 82 77 -5 WA
Curve Warning Sign with Flashers — flashing lights on sign  roadway departure rural 2-lane curve 25 (2005) 2 47 46 -1 51 50 -1
Static Signing
Chevron Signs — use of standard chevron signing roadway departure rural 2-lane 46 (2010) 2 70/45 & 50 adv. 57 55 -2 65 64 -1 1-mon TX
roadway departure rural 2-lane 25 (2005) 1 48 48 0 52 52 0 1-wk KY at PC
roadway departure rural 2-lane 46 (2010) 2 70/45 & 50 adv. 56 54 -2 65 63 -2 1-mon TX with full post delineation
Chevrons with Full Post Delineation roadway departure rural 2-lane 47 (2012) 4 50 to 55/35 to 50 adv. 50 50 0 56 55 -1 1-mon IA
Curve Sign + Flags roadway departure rural 2-lane 25 (2005) 3 46 45 -1 49 49 0 1-wk KY at PC
Arrow (MUTCD: W1-6)  roadway departure rural 2-lane 25 (2005) 1 43 44 1 46 47 1 1-wk KY at PC
Intersection Treatments
Roundabout— large, raised, circular islands at the middle of major intersections, around which all oncoming vehicles must traverse pedestrian rural 66 (2005) 19 20400 48 28 -20 MD, CA, WA, MI, Canada 
intersection suburban Y intersection (2-lane) 67 (2005) 1 5500 32 24 -8 1 to 3 years MI
intersection urban 68 (2005) 1 11000 to 12000 15500 47 33 -14 CO
Traffic Circle — circular, raised island placed within the middle of an intersection  intersection urban 1 (1999) 45 240 to 10910 269 to 8280 34 30 -4 TX, WA, CA, CO, NC, OH, OR, FL, GA, MD, NE, MA, MN, AZ
Access Control
Half-Closure pedestrian urban 1 (1999) 11 220 to 9540 151 to 9180 30 24 -6
Diagonal Diverter pedestrian urban 1 (1999) 7 474 to 2057 177 to 574 28 27 -1
Full Closure pedestrian urban 1 (1999) 2 1540 to 1980 850 to 1080 18 13 -3
Choker + Speed Hump pedestrian urban 1 (1999) 2 2456 to 3685 2593 to 2931 38 25 -13
Half-Closure + Median Barrier pedestrian urban 1 (1999) 2 10160 to 10320 1120 to 2120 38 32 -6
Gateway Entrance Treatments
Entrance Treatments — multiple treatments placed at community entrance to reduce speeds into community  pedestrian rural  community entrance  49 (2000) 1 40 45 41 -4 50 46 -5 1-mon United Kingdom red bars + signing + bulb-outs
pedestrian rural  community entrance  49 (2000) 1 20 35 24 -11 41 30 -11 1-mon United Kingdom narrowing + speed cushions
pedestrian rural  community entrance  49 (2000) 1 20 35 15 -10 41 30 -11 12-mon United Kingdom narrowing + speed cushions
pedestrian rural  community entrance  49 (2000) 1 30 40 30 -11 47 35 -13 1-mon United Kingdom red box + speed limit + dragon's teeth + signing
pedestrian rural  community entrance  49 (2000) 1 30 40 33 -8 47 38 -9 12-mon United Kingdom red box + speed limit + dragon's teeth + signing
Entrance Treatments — multiple treatments placed at community entrance to reduce speeds into community  pedestrian rural  community entrance 49 (2000) 1 30 38 33 -5 43 39 -4 1-mon United Kingdom red box + speed limit + dragon's teeth + signing
pedestrian rural  community entrance 49 (2000) 1 30 38 32 -6 43 36 -7 12-mon United Kingdom red box + speed limit + dragon's teeth + signing
pedestrian rural  community entrance  49 (2000) 1 30 41 39 -2 47 47 0 1-mon United Kingdom red patches + "SLOW" + dragon's teeth + signing 
pedestrian rural  community entrance  49 (2000) 1 30 41 37 -4 47 44 -3 12-mon United Kingdom red patches + "SLOW" + dragon's teeth + signing
pedestrian rural  community entrance  49 (2000) 1 40 51 45 -6 60 51 -9 1-mon United Kingdom red lines of decreasing size and width + signing
pedestrian rural  community entrance 49 (2000) 1 40 51 45 -6 60 53 -7 12-mon United Kingdom red lines of decreasing size and width + signing
pedestrian rural  community entrance  49 (2000) 1 40 44 39 -6 50 43 -7 1-mon United Kingdom red box + speed limit + signing 
pedestrian rural  community entrance  49 (2000) 1 40 44 38 -7 50 43 -7 12-mon United Kingdom red box + speed limit + signing

Notes: Information is presented to one significant digit unless the study only provided integer values. In some cases the study only provided resulting changes in speed rather than providing the actual before and after value.

Abbreviations

common state destinations are used and are not listed here (e.g. Iowa = IA)
advisory (adv)
intersection (isect)
month (mon.)
pedestrian (ped)
post mounted delineator (PMD)
rumble strips (RS)
run off road (ROR)
years (yrs.)

References

1.   Ewing, R. 1999. Traffic Calming: State of the Practice. Institute of Transportation Engineers, Washington, DC.

2.  ACV.  Effectiveness of Traffic Calming Measures in Arlington County.  Arlington County, VA. 2005. 

3.  Marek, J.C. and Walgren, S.  "Mid-Block Speed Control: Chicanes and Speed Humps."  City of Seattle, WA. 2000. www.seattle.gov/Transportation/docs/ITErevfin.pdf

4.  Ponnaluri, R.V. and P.W. Groce.  "Operational Effectiveness of Speed Humps in Traffic Calming."  ITE Journal.  2005.  pp. 26-30.

5.  Smith, D., S. Hallmark, K. Knapp, and G. Thomas.  Temporary Speed Hump Impact Evaluation.  Center for Transportation Research and Education at Iowa State University.  July 2002.

6.  Bretherton, W.M. "Do Speed Tables Improve Safety."  Presented at the 2003 Annual Meeting of the Institute of Transportation Engineers.  August 2003, Seattle Washington.

7.  Hallmark, S.L, E. Peterson, E. Fitzsimmons, N. Hawkins, J. Resler, and T. Welch.  Evaluation of Gateway and Low-Cost Traffic-Calming Treatments for Major Routes in Small Rural Communities, Phase I. Center for Transportation Research and Education, Iowa State University. Ames, Iowa. November 2007.  www.intrans.iastate.edu/research/projects/detail/?projectID=-226410767

8.  Corkle, J., J.L. Giese, and M.M. Marti. 2001. Investigating the Effectiveness of Traffic Calming Strategies on Driver Behavior, Traffic Flow, and Speed. Minnesota Local Road Research Board, Minnesota Department of Transportation. October 2001.

9.  NYCDOT.  Downtown Brooklyn Traffic Calming Study.  New York City Department of Transportation.  2004.

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11.  Molino, J.A., B.J. Katz, M.B. Hermosillo, E.E. Dagnall, and J.F. Kennedy.  Simulator Evaluation of Low-Cost Safety Improvements on Rural Two-Lane Undivided Roads:  Nighttime Delineation for Curves and Traffic Calming for Small Towns.  Science Applications International Corporation.  McLean, VA.  February 2010.

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