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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
FHWA Highway Safety Programs

Engineering Speed Management Countermeasures

eng_ctm_spd_14.pdf (636.96 KB)

A Desktop Reference of Potential Effectiveness in Reducing Speed

July 2014

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
Vertical Delineation
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.)

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