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Mn DOT Traffic Signal Timing and Coordination Manual of 240 vph for the subject Left turn. However, if the opposing Question 6 does include a threshold volumep . ume is low apply engineering judgment to determine if FYA operation could be used even if through vol� the left turn volume exceeds 240 vph. permissive FYA operation is If pallowed, •protected/permissive operation may be investigated. The decision to use protected/permissive operation should be based on a capacity analysis. Definitions Protected only left turn operation: signal phasing pal basin that allows left turn movements to only be made � on an exclusive pha5e (green arrow). ovationsgeometric constraints at the intersection cause the � Conflicting Left Turn Paths: At some I le is an paths of opposing left turn vehicles to cross as overlap creating a conflict. An exam p ` ided roadwaywith a wide median. In these locations, it may be necessary approach that crosses a divided to operate the left turns in a lead -lag sequence or a split phase sequence, not allowing simultaneous opposing left turns. This operation will require protected left turns. pp g The opposing through lanes are the lanes across from, and in 1 Opposing through lane (confllct): pp gva vote gaps in • nip vehicle. Multiple lanes make it difficult for a driver toe 1 g p conflict with, the left turning not be counted with opposing traffic. An opposing separate right turn lane will typically oncoming p through lanes unless engineering judgment indicates that the lane configuration and number of right turns will cause conflicts with the left turn movement, : The minimum sight distance values necessary for the design � Limited Sight Distance (Requ!remeflts) bar e the turn movement. Distance should be calculated fromthestop vehicle volume to complete and acceleration r N e left turningvehicle. Measurement is based on travel path,speed,. for the mainline sight distance for passenger vehicles and trucks should be checked using vehicle height. Both the p e current reference re �uirements per the heights and distanceg AASHTO Geometric Design Guide. Th at time this manualprepared was is the 2004 Guide, Chapter 9, Exhibit 9-67). Lanes: Multiple left turn lanes may consist of exclusive left turn lanes or• a 1 Dual Left Turn �, p •lanes and lanes that are shared by through and left turning traffic. combination of exclusive left turn operate the dual lane and the left turn lane opposing this operation are suggested to p orate with protected phasing. Left turnWay lanes without opposing traffic, such as left turns off of a one- way street, does not require protected phasing only based upon this criteria. It might also be possible to run the FYA in permissive mode during Iow volume times of the day. •operation: signal phasing that provides an exclusive phase (green � Protected/pern��ssive left turn p the signal cycle where bya permissive phase (flashing yellow arrow), time during g y arrow) followed p left turning traffic may make a left turn after yielding to oncoming traffic. These are Collisions that could be corrected by protected only phasing, � Left Turn Related Collisions: such as those between those involving a left turning vehicle and an opposing through vehicle. At . jcollisions are likel to be more severe. Therefore, a lower number of higher speeds the accidents Ymight be used as the parameter for consideration for high-speed approaches. Because of collisions mig the variations in collisions overtam • • e, an average number of collisions per year over a 3- year period should be used if the data is available. i i cult for a driver to accurately judge available gaps in traffic ,f Speed: Because it can be difficult approaching at high speeds, the engineer -must exercise discretion when considering permissive or permissive left turn phasing with opposing speeds of 45 MPH or above. protected perms �- - Pa eI3-30 Local Intersection Concepts May 2a 1�. g