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09/12/2016 Number ofLanes Traffic calming should only be used on streets with no more than two travel lanes. Streets with a center turn lane may still qualify far tr�c calming. Drainaee Characteristics Streets considered for traffic calming ahould have good drainage qualities. Potential drainage impacts must be considered when evaluating whether a traffic calming installation is appropriate. Street Grades Certain traffic calming measures should not be employed on streets with grades exceeding frve percent When traffic calming measures are installed on streets with sustained downgrades,special care should be taken to ensure that vehicles can navigate the installation safely at appropriate speeds. Si¢htDistance Traffic calming devices should generally be installed only where the minimum safs stopping sight distance(as defined in AASHTO's A Policy on Geometric Desrgn of Streets) can be provided. For mid-block locations on typical residential streets,a minimum safe stopping sight distance allowance would noimally be at least 200 feet,dienominal stopping sight diatance for vehicles traveling at 30 mph. Depending on the chazacter of the intersection and the traffic control, sight distance requirementa might be less for installations located within the influence area of an interaection. Traffic Soeeds When traffic calming is installed to address speeding concerns,studies will be performed to confurn the magnitude of the apeeding problem. The number ofvehicles exceeding apeed limits,percei►tage of all vehicles exceeding apeed timi�,85`�pacentile spead,and the apeed offaetestvehicles may all be considered when evaluating whether a speeding problem e�cists. Traffic calming devices should generally be inatallcd only on streets wheae the posted or prima facia speed limit ia 30 mph or leas. Where apeed problems occur on streets with higher speed litnits (such as stre�a posted for 35 mph experiencing 45-50 mph traffic), focused enforcement and combinations of other types of control measurea should be considered instead of apeed humps. Speed humps should only be used on streets where traffic speeds are intended to be low. Speed humps ahould not be installed on streets where the posted apeed limit is considerably greater than speeds at which most motorists feel comfortable iraversing the apeed humps. In Redwood City,spec�c criteria to qualify for haffic calming are as follows: • Eighty-fifth percentile speed exceeds 30 mph(35 mph on streeta posted 30mph), • 60 percent of the traffia exceeds the posted apeed limit(nrnmally 25 mph), • The average speed of vehicles in the top 15`"percentile is 40 mph or greater. Tramc Volumes Traffic calming should be installed only on streets classified as "Local Sireets", "Pedestrian Page 5 of 13 ATTY/RES0.0088/CC RESO TRAFFIC CALMING ON RESIDENTIAL STREETS RE50.N0.15522 REV:09-01-16 JS MUFF NO.702