Highway Capacity Manual Methodologies for Corridors Involving Freeways and Surface Streets (2020)

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378 A P P E N D I X G Glossary General Acronyms 𝐴𝑇𝐷𝑀 = Active Traffic and Demand Management; 𝐴𝑊𝑆𝐶 = all-way stop controlled intersection; 𝐷𝐷𝐼 = diverging diamond interchange; 𝐷𝑂𝑇 = Department of Transportation; 𝐸𝐵 = eastbound; 𝐹𝐻𝑊𝐴 = Federal Highway Administration; 𝐻𝐶𝑀 = Highway Capacity Manual; 𝐼𝐶𝑀 = Integrated Corridor Management; 𝐼𝑅𝑇 = interchange ramp terminal; 𝑀𝑂𝐸 = Measures of Effectiveness; 𝑁𝐵 = northbound; 𝑄𝐴𝑃 = queue accumulation polygon; 𝑆𝐵 = southbound; 𝑆𝑃𝑈𝐼 = single-point urban interchange; 𝑇𝑊𝑆𝐶 = two-way stop controlled intersection; 𝑊𝐵 = westbound. General Values 𝑑/𝑐 = demand to capacity ratio; 𝐸𝐷 = expected demand (veh/h); 𝑓 = adjustment factor for heavy vehicle presence; 𝐹𝐹𝑆 = free flow speed (mi/h); 𝐺 = grade (%); 𝐿𝑂𝑆 = level of service; 𝑂 − 𝐷 = origin-destination; 𝑃𝐻𝐹 = peak hour factor; 𝑃𝑀𝑇 = personal miles traveled (mi); 𝑣/𝑐 = volume/capacity ratio 𝑉𝑀𝑇 = vehicle miles traveled (mi).

379 1. Arterial Facilities 1.1. General concepts 𝑐 = merging capacity at the freeway (veh/h); 𝑐 = capacity of ramp proper (pc/h) (Eq. 38-2); capacity of the off-ramp roadway (pc/h) (Eq. 38-A1, 38-A3, 38-A6); 𝐿 = average vehicle spacing in stationary queue (ft/veh); 𝜆 = departure rate from the major-street left-turn into the on-ramp (veh/h); 𝜆 = total on-ramp demand throughput (pc/h); 𝜆 = departure rate from major street right turn into the on-ramp (veh/h); 𝜆 = departure rate from the minor street through into the on-ramp (veh/h); 𝑄 ,( ) = 95th percentile of queue, where (a) = approach direction (veh); 𝑠 = saturation flow rate of movement 𝑖 (veh/h/ln); 𝑣 = maximum entering flow rate for the intersection approach (veh/h); 𝑥( ) = volume-to-capacity ratio for approach direction a 1.2. Signalized Intersections 𝑐 = capacity for approach 𝑖 (veh/h); 𝑔 = green extension time (s); 𝑔 = green service time (s); 𝑙 = start-up lost time (s); 𝑙 = clearance lost time (s); 𝑁 , = total number of vehicles discharged from each protected movement 𝑖; 𝑁 , = total number of vehicles discharged from each permitted movement 𝑖; 𝑁 , , = total number of vehicles discharged for movement 𝑖 during the green extension time; 𝑁 , , = total number of vehicles discharged for movement 𝑖 during the queue service time; 𝑞 = arrival flow rate during the effective green time = 𝑃 𝑞 𝐶/𝑔 (veh/s); 𝑟 = effective red time (s); 𝑅 = platoon ratio; 𝑋 = demand-to-capacity ratio for spillback conditions. 1.3. TWSC Intersections cm,j = movement capacity for movement i (Equations 20-36, 20-37 and 20-40). cSB,i = capacity during spillback for movement i (veh/h) cEQ,i = adjusted capacity for movement i (veh/h) N(t) = number of queued vehicles along the on-ramp at time t; T = duration of analysis time period (minutes)

380 TSB = time period with active spillback (minutes) 1.4. AWSC Intersections 𝑐 , = potential capacity for the minor street through (veh/h); cSB,i = capacity during spillback for movement i (veh/h) cEQ,i = adjusted capacity for movement i (veh/h) N(t) = number of queued vehicles along the on-ramp at time t; T = duration of analysis time period (minutes) TSB = time period with active spillback (minutes) ℎ = departure headway during queue spillback (s/veh); 1.5. Roundabouts 𝜆( ), = maximum throughput for (a) movement (pc/h); 𝑐 ,( ) = entry lane capacity for roundabout approach, where (a) = approach direction (pc/h); 𝑑( ) = average control delay for (a) approach (sec/veh); 𝑑 = additional delay due to on-ramp spillback (sec/veh); ℎ , = departure headway for the major street left turn (s); ℎ , = departure headway for the major street right turn (s); ℎ , = departure headway for the minor street through (s); ℎ = departure saturation headway into the on-ramp (s/veh); p(a)-ONR = percent of demand from NB approach a into the on-ramp 𝑄 = expected queue length QSP along the on-ramp during a 15-minute period analysis; 𝑄 = total number of vehicles queued during a 15-minute time period analysis; 𝑣( ), = flow rate for roundabout approach a (veh/h) 𝑣 ,( ), = circulating flow rate for roundabout approach a (veh/h) 𝑣 ,( ), = entry flow rate for roundabout approach a (veh/h) total number of vehicles queued during a 15-minute time period analysis 2. Freeway Facilities 2.1. Lane by lane analysis ∆𝑁𝑉(𝑖, 𝑡,𝑝)= additional density of segment 𝑖 at the end of time step 𝑡 during time interval 𝑝 (veh/mi/ln); 𝐿𝐹𝑅 = lane flow ratio; 𝑎 = empirical constant; 𝐵𝑃 = breakpoint value; 𝑐 = empirical constant; 𝐶𝐴𝐹 = capacity adjustment factor for the upstream freeway area; 𝑓 = adjustment factor for 𝑎; (Eq. 38-3, 38-C2, 38-C3, 38-C5, 38-C7)

381 𝑓 , = adjustment factor for 𝑎; due to impact of grade; 𝑓 , = adjustment factor for 𝑎; due to impact of interchange density; 𝑓 , = adjustment factor for 𝑎; for length of the weaving segment; 𝑓 , = adjustment factor for 𝑎; due to impact of access point density; 𝑓 , = adjustment factor for 𝑎; due to impact of trucks; 𝑓 , = adjustment factor for 𝑎; for off-ramp flow; 𝑓 , = adjustment factor for 𝑎; for on-ramp flow; 𝑓 , = adjustment factor for 𝑎; due to impact of ramp flow; 𝑓 , = adjustment factor for 𝑎; for volume ratio; 𝑓 = adjustment factor for 𝑐; (Eq. 38-3, 38-C2, 38-C4, 38-C6, 38-C8) 𝑓 , = adjustment factor for 𝑐; due to impact of grade; 𝑓 , = adjustment factor for 𝑐; due to impact of interchange density; 𝑓 , = adjustment factor for 𝑐; for length of the weaving segment; 𝑓 , = adjustment factor for 𝑐; due to impact of access point density; 𝑓 , = adjustment factor for 𝑐; due to impact of trucks; 𝑓 , = adjustment factor for off-ramp flow; 𝑓 , = adjustment factor for on-ramp flow; 𝑓 , = adjustment factor due to impact of ramp flow; 𝑓 , = adjustment factor for volume ratio; ℎ = reaction headway (s); 𝐼𝐷 = interchange density (veh/mi/ln); 𝐾𝐵 = background density (veh/mi/ln); 𝑛 = access point density – number of ramps half a mile upstream and half mile downstream (veh/mi/ln); 𝑡 = truck percentage (%); 𝑣 = segment entering demand (pc/h); 𝑣 = ramp flow for freeway analysis (veh/hr); 𝑣 , = off-ramp flow for freeway analysis (veh/hr); 𝑣 , = on-ramp flow for freeway analysis (veh/hr); and 𝑉𝑅 = volume ratio (weaving volume/total volume). 2.2. Off-ramp queue spillback 𝑐 = capacity of ramp proper (pc/h) (Eq. 38-2); capacity of the off-ramp roadway (pc/h) (Eq. 38-A1, 38-A3, 38-A6); 𝑓 = adjustment factor for driver population; 𝐾𝐵𝐵𝐿(𝑖, 𝑡,𝑝) = background density (pc/mi/ln) of the blocked portion of segment 𝑖 during time step 𝑡 in time interval 𝑝; 𝐾𝐵𝑈𝐵(𝑖, 𝑡,𝑝) = background density (pc/mi/ln) of the unblocked portion of segment 𝑖 during time step 𝑡 in time interval 𝑝; 𝐿 = section 𝑖 length (ft); 𝐿 (𝑖,𝑝) = available deceleration lane length (ft) for segment 𝑖 during time period 𝑝; 𝐿 , 𝐿 = available queue storage distance (ft/ln); 𝐿 = length of the weaving segment (ft);

382 𝐿𝐹𝑅 = share of the total flow on lane 𝑖 𝑂𝐹𝑅𝐹(𝑖, 𝑡,𝑝) = actual flow that can exit at off-ramp 𝑖 during time step 𝑡 in time interval 𝑝 (veh/h); 𝑂𝑁𝑅𝑂(𝑖, 𝑡,𝑝) = maximum output flow rate that can enter the merge point from on-ramp 𝑖 during time step 𝑡 in time interval 𝑝 (veh/h); 𝑂𝑁𝑅𝑄 = onramp queue length (veh); 𝑀𝐹𝐵𝐿(𝑖, 𝑡,𝑝) = mainline flow rate that can cross the blocked portion of node 𝑖 during time step 𝑡 in time interval 𝑝; 𝑀𝐹𝑈𝐵(𝑖, 𝑡,𝑝) = mainline flow rate that can cross the unblocked portion of node 𝑖 during time step 𝑡 in time interval 𝑝; 𝑀𝐼𝐵𝐿(𝑖, 𝑡,𝑝) = maximum flow desiring to enter the blocked portion of node 𝑖 during time step 𝑡 in time interval 𝑝; 𝑀𝐼𝑈𝐵(𝑖, 𝑡,𝑝) = maximum flow desiring to enter the unblocked portion of node 𝑖 during time step 𝑡 in time interval 𝑝; 𝑀𝑄1(𝑖, 𝑡,𝑝) = mainline queue length of off-ramp unserved vehicles in the rightmost mainline lane, for segment 𝑖 during time period p in time interval 𝑡; 𝑀𝑄2(𝑖, 𝑡,𝑝) = mainline queue length of off-ramp unserved vehicles in the rightmost mainline lane, for segment 𝑖 during time period p in time interval 𝑡; 𝑁 , = number of lanes in section 𝑖 that are associated to ramp lane 𝑘; 𝑁 = number of approaching lanes for lane group 𝑚; 𝑁𝑉 = number of vehicles (veh); 𝑁𝐸𝑋𝑇𝑂𝐹𝑅(𝑖) = index of the nearest downstream diverge segment relative to subject node 𝑖; 𝑂𝐹𝑅𝐷𝐼𝑆𝑇(𝑖) = distance (ft) from node 𝑖 to the start of the deceleration lane at the nearest downstream off-ramp; 𝑂𝐹𝑅𝐿𝑄(𝑖, 𝑡,𝑝) = queue length of off-ramp unserved vehicles for diverge segment 𝑖 during time period 𝑝 in time interval 𝑡; 𝑂𝐹𝑅𝐹𝑈𝑃(𝑖, 𝑡,𝑝) = flow that can exit at the closest off-ramp downstream of 𝑖 during time step 𝑡 in time interval 𝑝; 𝑂𝐹𝑅𝑈𝑉(𝑖, 𝑡,𝑝) = number of off-ramp unserved vehicles for segment 𝑖 during time period p in time interval 𝑡; 𝑄 = queue growth during analysis period 𝑖 (pc); 𝑄𝐼𝐴(𝑖,𝑝) = length of the queue influence area (ft) for segment 𝑖 during time period 𝑝 (ft); 𝑄 , = number of queued vehicles in Ramp Lane 𝑘, during a 15-min interval (pc); 𝑄 , = number of queued vehicles from Lane Group 𝑚 associated with ramp lane 𝑘, during a 15-min interval (pc); 𝑄 = maximum queue length on the ramp (pc); 𝑄 %, = estimated back of queue length (nth percentile), as defined in Equation 31-150 (veh/ln); 𝑄 = length of queue beyond ramp storage distance (ft); 𝑄 = queue length during for the analysis period 𝑡 (pc); 𝑅 = on-ramp storage ratio (veh); 𝑅𝐶(𝑖,𝑝)= Capacity of the ramp proper (pc/h) during time period 𝑝 in time interval 𝑡; 𝑅𝐹(𝑖, 𝑡,𝑝) = flow (pc/ts) that can enter the ramp proper at segment 𝑖 during time period p in time interval 𝑡; 𝑅𝐼(𝑖, 𝑡,𝑝) = maximum flow (pc/ts) desiring to enter the off-ramp on segment 𝑖 during time period 𝑝 in time interval 𝑡; 𝑅𝐾𝐵(𝐼, 𝑡,𝑝) = ramp proper queue density (pc/mi/ln) for segment 𝑖 during time period p in time interval 𝑡; 𝑅𝐾𝐶 = ramp density at capacity (pc/mi/ln); 𝑅𝐿(𝑖) = length of ramp proper (ft) for segment 𝑖; 𝑅𝑀(𝑖, 𝑡, 𝑝) = metering rate at on-ramp 𝑖 during time step 𝑡 in time interval 𝑝 (veh/h); 𝑅𝑁(𝑖) = number of ramp lanes for segment 𝑖; 𝑅𝑁𝑉(𝑖, 𝑡,𝑝) = maximum number of vehicles (pc) within the ramp of segment 𝑖 at the end of time step 𝑡 during time interval 𝑝; 𝑅𝑈𝑉(𝑖, 𝑡,𝑝) = number of unserved vehicles at the entrance of the ramp proper of segment 𝑖 at the end of time step 𝑡

383 during time interval 𝑝; 𝑆 = number of computational time steps in an analysis period; 𝑠 = measured speed at the beginning of congestion at the upstream detector (mi/h) 𝑆𝐵𝐾𝑄 (𝑖, 𝑡,𝑝) = spillback queue density for segment 𝑖 during time period 𝑝 in time interval 𝑡; 𝑆𝐵 (𝑖, 𝑡,𝑝) = capacity adjustment when one or more lanes of segment 𝑖 are entirely blocked during time period 𝑝 in time interval 𝑡; 𝑆𝐵 (𝑖, 𝑡,𝑝) = capacity adjustment factor for approaching vehicles within the queue influence area upstream of an off- ramp queue; 𝑆𝐵𝐿𝐶(𝐼, 𝑡,𝑝) = number of lane change maneuvers within the Queue Influence Area at node 𝐼, during time step 𝑡 in time interval 𝑝; 𝑆𝐵𝐿𝑄(𝑖, 𝑡,𝑝) = queue length within segment 𝑖 during time period 𝑝 in time interval 𝑡; 𝑆𝐿(𝑖,𝑝) = available shoulder length (ft) for segment 𝑖 during time period 𝑝; 𝑇𝐼𝐴 = total influence area (ft); 𝑣 = on-ramp flow rate (veh/h) (Eq. 38-B10); off‐ramp demand for the period (pc/h) (Eq. 38-A1, 38-A3, 38- A6);