Speed Control Measures
Active Measures - includes vertical deflection, horizontal deflection, and constrictions
Speed hump Raised pavement hump installed across the traveled lanes, typically 3 to 4 inches high and 22 feet long. Speed hump use is strictly limited to retrofit situations, not new construction.
Raised crosswalk Raised pedestrian crossing placed in the road and extending across the road at right angles to traffic flow, typically 3 to 4 inches high. Raised crosswalks provide greater visibility for both the pedestrian and motorist.
Raised intersection Raised intersections, including crosswalks, typically 3 to 6 inches high, with ramps on all approaches.
Roundabout Raised circular island in the center of an intersection that directs vehicles to travel counterclockwise around the circle, reducing vehicle speeds. Roundabouts should be constructed in such a fashion as to allow large types of vehicles, such as fire and rescue apparatus along with trucks, buses, and vans to traverse around the island.
Neighborhood traffic circle Raised circular island, placed at multi-way intersections in residential areas that force vehicles to slow down to negotiate around it.
Chicane Series of fixed objects, usually curb extensions, staggered at mid-block locations that alter a straight roadway into a serpentine path to slow vehicles.
Realigned intersection Changes in alignments that convert T-intersections with straight approaches into curving roadways meeting at right angles.
Center island median Raised island between travel lanes that narrows the lane widths at that location.
Curb extension/neck down Curb extension, usually at intersections, that narrows the roadway width and inhibits fast turns.
Choker Curb extensions or islands, placed either at an intersection or mid-block location that narrows the lane widths.
Gateway Special entrance treatments that may include alterations in the pavement surface, such as stamped asphalt or concrete, etc., that alerts motorists they are entering a neighborhood that requires lower speeds.
Pedestrian refuge island Raised island, at mid-block location or intersection, between travel lanes, with openings in the landscaping or curbing for pedestrians.
Passive Measures - includes on-street parking, bicycle lanes, streetscape, SMART trailer (speed awareness trailer), signing and striping, forced perspective, and colored pavements.
On-street parking Parking lanes on one or both sides of the roadway, providing a visual and physical narrowing of the street.
Bicycle lanes Lane where bicyclists can travel outside the normal travel lane. “Share the Road” design may also be implemented in areas of bicycle use.
Streetscape Aesthetic enhancements that provide a psychological message to motorists to slow down.
SMART trailer Speed awareness trailer used by the Carroll County Sheriff’s department.
Speed awareness signs Speed awareness radar signs placed by the County.
Signing and striping Painting of travel lanes, parking lanes, directional markings, crosswalks and addition of signs. Stop signs are used to determine normal vehicle right-of-way rules, and will not be used as a traffic calming measure.
Volume Control Measures
Street closure Physical barrier placed across a street obstructing all traffic movements, usually leaving only sidewalks or bicycle paths open.
Partial closure Physical barrier that blocks travel in one direction for a short distance on an otherwise two-way street.
Diagonal diverter Physical barrier placed diagonally across an intersection preventing through movement.
Median barrier Raised island between travel lanes through an intersection that prevents through movement at a cross street.
Forced turn island Raised island used on approaches to an intersection that prevents certain movements.


The County will install all the appropriate signs and pavement markings when any traffic calming measure is placed. Signs and pavement markings will comply with the MUTCD where applicable.
The Board of Education, local law enforcement agencies, and local fire departments will be involved as part of the process to ensure that recommendations of physical traffic calming measures do not hamper the agencies’ abilities to perform their respective duties.
The County will assess the probability that installing physical traffic calming measures on a street would divert traffic to another residential street. If significant diversion is probable, those streets affected by the diversion will be identified and also assessed for possible physical and non-physical devices.