FLH PDDM Chapter 9 - Eastern Federal Lands Highway Division

9.4.B. Intersection Design. (continued)The SU vehicle serves as the design vehicle for most rural highway conditions, including most recreationalroads. If there is significant semi-truck traffic, use the WB-15 or WB-19 vehicles. In areas where SU or WBvehicles are not prevalent, and ROW restrictions prohibit adequate sight triangle clearing, the P design vehiclemay be applicable.At some intersections the turning volume from a stop-controlled minor roadway is significant enough toconflict with through vehicles on the major roadway. In these instances, sight distances shown in Table 9-11are recommended. The distances shown in the table for P or SU design vehicles are the sight distancesrequired for P vehicles to turn onto a two-lane highway and attain an average running speed without beingovertaken by a vehicle going the same direction. The distances shown in the table for the WB-15 and WB-19design vehicles are the sight distances required for them to complete a left turn. Using sight distances less thanthat required for the P or SU vehicle will require the through traffic to reduce speed.For additional information on sight distance and for sight distance across divided highways, refer to Chapter IXof the Green Book.Table 9-11Sight Distance for Turning VehiclesDesign SpeedDesign Vehicle(km/h) P or SU WB - 15 WB - 1930 110 130 15040 120 155 18050 145 195 22560 160 235 27070 235 270 31580 315 315 36590 395 395 405100 475 475 475110 565 565 5655. Channelization. Channelization separates traffic into definite paths of travel using pavement markings orraised islands. Channelization facilitates the safe and orderly movement of vehicles, bicycles, and pedestrians.Pavement markings used to delineate travel paths generally consist of painted stripes reflectorized with glassbeads. Raised Pavement Markers (RPM), reflectorized and nonreflectorized, may supplement pavementstriping when increased visibility is desirable. RPM may replace painted stripes when climatic or trafficconditions warrant. (See Chapter 8).Curbing is permissible for channelization under the following conditions:Prevention of mid-block left turns.Raised divisional and directional islands.Raised islands with luminaries, signals, or other traffic control devices.Pedestrian refuge islands.Landscaped areas within the roadway.Curbing is undesirable at any location where painted pavement markings with or without reflective lanemarkers attain the same objective.9 - 61