![]() ![]() c p,x = Potential capacity of minor movement x (veh/h).c subscript p, x is equal to the product of v subscript c,x, times the quotient of the exponential function of open parenthesis negative v subscript c,x, times t subscript c,x divided by 3600, close parenthesis divided by the following: 1 minus the exponential function of open parenthesis (negative v subscript c,x, times t subscript f,x, divided by 3600, close parenthesis. Lane Group Capacity for Roundabouts and Stop Controlled Intersections. The following equation is used to compute the lane group capacity for the approach to a roundabout and for a stop sign controlled approach to an intersection:Įquation 5. f Rpb = Pedestrian-bicycle adjustment factor for right-turn movements.f Lpb = Pedestrian adjustment factor for left-turn movements.f RT = Adjustment factor for right turns in lane group.f LT = Adjustment factor for left turns in lane group.f LU = Adjustment factor for lane utilization.f bb = Adjustment factor for blocking effect of local buses that stop within intersection area.f p = Adjustment factor for existence of a parking lane and parking activity adjacent to lane group.f g = Adjustment factor for approach grade.f HV = Adjustment factor for heavy vehicles in traffic stream.f w = Adjustment factor for lane width.s o = Base saturation flow rate per lane (pc/h/ln).g/C = Effective green time per cycle ratio for lane group. ![]() cap = Capacity for subject lane group, expressed as a total for all lanes in lane group (veh/h).S = (g/C) s o N f w f HV f g f p f bb f a f LU f LT f RT f Lpb f Rpb The following equation is used to compute the lane group capacity for an approach to a signalized intersection: Due to the discontinuous nature of the procedure for weaving sections, no closed form equation for capacity is available. f g = Adjustment factor for grades (used for two-lane highways only).įor freeway and highway weaving sections the capacity is a function of weaving type, number of lanes, free-flows speed, length and weaving ratio.f p = Driver population adjustment factor (used for freeway and multilane only).PHF = Peak-hour factor (the ratio of the peak 15-minute flow rate to the average hourly flow rate).f hv = Heavy vehicle adjustment factor (varies by facility type, vehicle mix, and grade).Base Cap = Base capacity in terms of passenger cars per hour per lane (varies by facility type).Cap = Capacity in terms of vehicles per hour.The following equation is used to compute the capacity of all uninterrupted flow facilities (freeways, multi-lane highways, and two-lane rural roads):Ĭap = Base Cap * N * f hv * PHF* f p * f g The HCM defines capacity as "The maximum sustainable flow rate at which vehicles or persons reasonably can be expected to traverse a point or uniform segment of a lane or roadway during a specified time period under given roadway, geometric, traffic, environmental, and control conditions…" The HCM capacity for each facility type is computed according to the equations below. The HCS software computes capacity per the HCM method. HCS implements the following HCM methods: Signalized Intersections, Unsignalized Intersections, Urban Streets, Freeway Basic, Freeway Weave, Freeway Ramps, Freeway Facilities, two-lane Rural Roads, Multi-lane Rural Highways, and Transit. As such, excepting for programming errors, which are corrected as soon as they are found, the HCS software computes the HCM LOS exactly according to the HCM methods. The HCS software is intended to be a faithful implementation of the Highway Capacity Manual. The section describes how the MOEs are computed by the HCS software, Version 5.2, developed by the University of Florida, in 2005. This section describes the methodologies used by the operations analysis tools to compute the MOEs that were selected for further investigation in Chapter 2. 4.1 Description of MOE Computation Methodologies Variations in the reported MOEs are noted. Then the tools are tested on a simple test bed under both free-flow and congested traffic demand conditions. First the computation methodologies are explained based upon published user guides for each tool and informal correspondence with the software developers. This chapter presents the results of a comprehensive investigation into how commonly used traffic analytical tools define and calculate commonly used MOEs. Traffic Analysis Tools Measures of Effectiveness 4.0 Calculation of MOEs by Traffic Analytical Tools Table of Contents Traffic Analysis Toolbox Volume VI:ĭefinition, Interpretation, and Calculation of ![]()
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