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Suggested Citation:"GLOSSARY." Transportation Research Board. 1997. Capacity Analysis of Interchange Ramp Terminals: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6350.
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Suggested Citation:"GLOSSARY." Transportation Research Board. 1997. Capacity Analysis of Interchange Ramp Terminals: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6350.
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Suggested Citation:"GLOSSARY." Transportation Research Board. 1997. Capacity Analysis of Interchange Ramp Terminals: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6350.
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GLOSSARY A= (iact °2r SIX = be b,, b2, b3= C= C, = CP = C = Cry, = D= difference between the actual and ideal signal offset, see; variance obtained from a regression analysis (i.e., = root mean square error21. variance in data due to random sources; variance in the independent variable; calibration coefficients; cycle length, see; capacity of lane i (estimated as ci ' = G /Hi ), vpcpl; clear period during cycle/phase when subject flow is urlblocked, see; capacity of the lane group, vpc; critical lane volume of lane group i, v phpl; effective distance to the back of downstream queue (or stop line if no queue) at start of subject (or upstream) phase, m; D,72 w = average maneuver distance for weaving vehicles (= tw - [g w), m, al,,, i = maneuver distance for vehicle i, m; ffv',n~ = distribution ofthe maximum demand flow rate in any of Planes; fin = adjustment factor for bus blockage; fD = adjustment factor for distance to downstream queue at green onset; fg = adjustment factor for approach grade; for = adjustment factor for signal timing; fHV= adjustment factor for heavy vehicles; fit= adjustment factor for left-t~s in lane group, fp = adjustment factor for parking; fpp = adjustment factor on delay depending on platoon arrivals, fR = adjustment factor for radius of travel paw; fRT= adjustment factor for right-turns in lane group; fu= fly= fw= G= proportion of drivers that do not attempt to evenly distribute themselves, adjustment factor for volume level (i.e., traffic pressure), adjustment factor for lane width; green signal interval, see, g = effective green time where platoon saturation flow can occur at stopline, see; G,,~ = maximum green signal interval duration for the subject (or upstream) phase that allowable without spilIback during saturated flows, see; go = maximum g/C ratio (larger g/C ratios have no additional effect on headway); gY = or _ - he = rr _ hi = rr j ~ O ~ v =7 _ _ On effective green extension into yellow warning interval, see; minimum discharge headway, sec/veh; clearance headway between last queued vehicle and first alTiving vehicle, see; minimum discharge headway in lane i, sec/veh, headway of the vehicle in He ith queue position, see; minimum discharge headway based on specification of the jth queue position as the first to achieve minimum discharge headway, sec/veh; H', = left-turn movement minimum discharge headway, sec/veh, x

H,h = through movement minimum discharge headway, sec/veh; r _ lg- ~ _ AL T _ Up- r_ 15 - indicator variable (1.0 if g/C < go, 0.0 otherwise); indicator variable (1.0 if Dm w > 90 by, - 1), 0.0 otherwise); indicator variable (1.0 if Ma~c(v~dl, v'd,)/v' > 1/N, 0.0 otherwise); indicator variable (1.0 if spillback occurs during phase, 0.0 otherwise), indicator variable (1.0 if Xi > be, 0.0 otherwise), last queue position to discharge, "specified" first queue position to discharge at minimum discharge headway, distance between subject and downstream intersection stoplines (i.e., link length), m; clearance lost time at end of phase, see; lane length occupied by a queued heavy vehicle (~ 13 m/veh), m/vein, lane length occupied by a queued passenger car (= 7.0 m/pc), m/pc; average length of queue joined by weaving vehicles, m, length of queue joined by vehicle i, m; start-up lost time based on Hj, see; start-up lost time to attain saturation flow, see; average lane length occupied by queued vehicle, m/vein, distance between off-ramp entry point and stop line of downstream intersection (i.e., length of weaving section), m; larger of v 'Q., and v dr number of lanes in lane group; number of through lanes on downstream segment, lanes; number of vehicles in queue on downstream street segment at end of phase, vein; number of vehicles on downstream street segment (moving or queued) at start of the subject phase, vein, X, = number of arsenal through lanes in the subject direction, lanes; 0~a = actual offset between subject phase and downstream Trough movement (phase start time downstream minus phase start time upstream), see; ideal offset to ensure progression without speed disruption, see; portion of heavy vehicles in the traffic stream; portion of left-turns in the larle group, portion of nght-turns in Me lane group; probability of a weaving vehicle being unblocked; average phase capacity at interchange I per lane, vphpl; radius of curvature of We left-turn travel path (at center of path), m; total interchange overlap at four-phase signalized interchange, see; R2 value obtained from a regression analysis; MaDCfV fib, V~J= N= Nd = nj = ns = oft= PHV PLT PRT Pu= Pil = R= Hi= R2ac! = R2~,est = largest possible R2 value obtainable (i.e., all systematic error explained); RC = red clearance interval, see; s = saturation flow rate for the lane group under prevailing conditions, vphg; so = saturation flow rate per lane under ideal conditions, pcphgpl; sj = saturation flow rate for the subject lane based on specification of the jth queue position as the first to achieve the minimum discharge headway, vphgpl; AL = approach speed limit, lan/h; s, = saturation flow rate per lane under prevailing conditions; vphgpl; X1

Sn = saturation flow rate for the subject lane under prevailing conditions assuming the "no-spilIback" condition, vphgpl; so = saturation flow rate for the subject lane under prevailing conditions assuming the "with-spiliback" condition v~haol: , ,. in, , T = duration of HCM delay analysis period, hours, discharge time of the pith queued vehicle, see, discharge time of the ith queued vehicle (i = j-] to by, see; signalization variable (0.0 < tg < go); time of evens j for vehicle i (7 = entry, stop, exit), see, maneuver time for vehicle i, see; relative signal offset from upstream signal i to downstream signals, see; lane utilization factor for the lane group; average arterial speed entering the weaving section, m/s, average maneuver speed for arterial Trough vehicles, m/s; average maneuver speed for weaving vehicles, m/s; maneuver speed for vehicle i, m/s; lane utilization factor for preposition~ng; lane utilization factor for random lane-choice decisions; us = speed at saturation flow, m/s; Va = average arsenal flow rate entering the weaving section, vph, vg' = unadjusted demand flow rate for the laIle group, vpc, v;' = demand flow rate in lane i, i = I, 2, N. vpcpI, v,' = demand flow rate per lane (i.e., traffic pressure), vpcpI, v,' = demand flow rate per lane, vpcpl; V ~ . . w v V dl average weaving Ilow rate, vph; demand flow rate for the lane group, vpc; flow rate in lane group mining left at We downstream intersection, vpc; V 'dear = flow rate in lane group turning right at the downstream intersection, vpc, 'snare = maximum demand flow rate in any of N lanes, vpcpl; X= volume-to-capacity ratio for the lane group; Xi = volume-to-capacity ratio in lane i, i = I, 2, ..., N; and Y= yellow warning interval, sec. · - X11

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