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71 APPENDIX A Glossary Adjusted flow rates--The maximum rate of flow adjusted Commercial vehicles--Vehicles transporting airline passen- for traffic conditions, traffic composition, roadway geometry, gers and visitors, including taxicabs, limousines, courtesy vehi- and other factors. cles, buses, and vans, driven by professional drivers for which vehicle passengers pay a fee or for which the transportation is Air taxi--A for-hire passenger or cargo aircraft that operates incidental to the service provided (e.g., a hotel courtesy vehicle). on an unscheduled basis. Cost path--A person's perceived cost that would be incurred Airfield licenses--Licenses or permits required to operate a while traveling along a defined path or route, typically includ- ground transportation vehicle on an airfield at major airports. ing the value of time. Airport curbside--The one-way roadway located immedi- Courtesy vehicles--Door-to-door, shared-ride transportation ately in front of the terminal building where vehicles stop to provided by the operators of hotels/motels, rental car compa- pick up and drop off airline passengers and their baggage. nies, parking lots, and other services solely for their customers. Automatic traffic recorder (ATR)--Equipment, often porta- Critical movement analysis--An analysis conducted to cal- ble, that records the volumes of traffic crossing a pneumatic culate the lanes or movements requiring the most "green tube or detector. time" at a signalized intersection and, therefore, a method of Automatic vehicle identification (AVI)--Radio frequency estimating the intersection volume to capacity (v/c) ratio. identification equipment (i.e., vehicle-mounted tags or trans- Critical volumes--The volume or combination of vol- ponders) commonly used on roadways and bridges to collect umes (e.g., conflicting movements) that produces the high- tolls. est demand for an intersection lane or signal phase. Auxiliary lane--A supplementary lane intended to facilitate Curbside geometry--The horizontal and vertical alignment weaving or merging vehicle movements between a roadway features of a curbside roadway, including lane widths, grades, entry and exit. curvature, and crosswalks. Bypass lanes--Curbside roadway lanes intended for use by Customs and Border Protection (CPB)--The U.S. govern- vehicles bypassing or not stopping at a curbside section or ment agency responsible for, among other duties, inspection zone. of international arriving passengers and goods to collect Bypass vehicles--Vehicles traveling past, but not stopping import duties and prevent the import of illegal goods. at, a curbside section or zone, including vehicles recirculating Decision-making distance--The physical distance between past the curbside, vehicles traveling to/from adjacent curb- successive decision points. side zones, or service/delivery vehicles using the curbside roadway. Decision point--The physical location where a driver must select between alternative paths or roadways. Cell phone lots--Free parking lots, typically located away from the terminal area, provided for use by motorists waiting Deplaned passengers--Passengers that alighted from an air- to pick up deplaned passengers. Also referred to as "call-and- craft at an airport, including both connecting and terminat- wait" or "park-and-call" lots. ing airline passengers.

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72 Discount factor--An adjustment applied to reduce the effec- Immigration and Customs Enforcement (ICE)--The U.S. tive capacity of curbsides with an unusual configuration, loca- government agency responsible for, among other duties, tion, or operation. inspection of international arriving passengers and crew prior to their entering the country. Double parking--A condition in which two or more vehicles are parallel parked or stopped adjacent to one another along Intelligent transportation system (ITS)--Information and the curbside roadway. communication technologies applied to transportation infra- structure and vehicles to improve operations, safety, and Driver population factor--A factor applied to roadway capac- efficiency. ities to reflect driver behavior and operating characteristics, including familiarity with roadways, intersections, and traffic Intersection Capacity Utilization (ICU) method--As used patterns. in this Guide, a quick-estimation method for analyzing inter- Electronic ticketing kiosk--A self-serve machine used by air- sections using the critical movement analysis. line passengers to print boarding passes and other documents. Lag time--The length of time after a flight's scheduled arrival Enplaned passengers--Passengers who boarded an aircraft at time that a passenger arrives at the airport curbside. an airport, including both connecting and originating airline Landside circulation system--The airport roadway network passengers. providing for inbound and outbound traffic and the internal Fixed-base operator (FBO)--An aviation business that serves circulation of traffic between airport land uses. general aviation aircraft owners and operators, including Lane balance--A situation that exists when the number of fueling, catering, aircraft maintenance, and storage. lanes entering a roadway is equal to the number of lanes exit- Flattening the peak--A reduction in the proportion of demand ing the roadway. occurring in a 15-minute or hourly interval as a result of de- Lane geometry--The horizontal and vertical alignment fea- mand management, changes in schedules, demand approach- tures of a roadway or roadway lane, including lane widths, ing capacity, or other reasons. grades, lengths, curvatures, tapers, and other physical features. Free-flow speed--The mean speed of traffic under very light Lateness distribution--The distribution of passengers leav- flow conditions. ing an airport after the scheduled arrival time of their aircraft General aviation--All flights (or aircraft operations) other (i.e., a distribution of passenger lag times). than scheduled/commercial or military flights. Lead time--As used in this Guide, the length of time in advance Gore--The triangular area between two roadways at the point of a flight's scheduled departure time that a passenger arrives they diverge or merge. at the airport curbside. Green time--The duration, in seconds, of the green indication Macroscopic models--Models or analytical procedures used for a given movement at a signalized intersection. to consider the flow of vehicle streams (or other objects) rather Growth factor--A factor applied to passenger or traffic vol- than the flow of individual vehicles. umes, for example, to adjust for anticipated future growth. Manual of Uniform Traffic Control Devices (MUTCD)-- Heavy vehicle--A vehicle with more than four wheels touch- The principal standard governing the application, design, and ing the pavement during normal operation. placement of traffic control devices, published by FHWA. See http://mutcd.fhwa.dot.gov. Heavy vehicle factor--A factor applied to roadway capacities to reflect the proportion of heavy vehicles in the traffic stream. Maximum service flow--A maximum flow rate at which vehi- cles can traverse a point or short segment during a specified Highway capacity analysis procedures--Analytical proce- time period at a given level of service. dures conducted using the procedures described in the Highway Capacity Manual. Merging capacity--Maximum flow rate at a merge point. Highway Capacity Manual (HCM)--The Highway Capacity Metropolitan planning organization (MPO)--A policy- Manual published by the Transportation Research Board, making organization responsible for planning, analysis, National Research Council, 2000 (and subsequent editions, and development of multimodal transportation facilities in including the draft 2010 HCM). a region or community.

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73 Microsimulation models--Models or analytical procedures Terminal area roadways--The roadways serving the termi- used to simulate the operation of individual vehicles (or other nal building and surrounding areas, including access, curb- objects) on simulated roadway (or other) networks. side, and circulation roadways. Mixed-flow traffic volumes--The numbers of vehicles in a Through vehicles--As used in this Guide, vehicles bypassing traffic flow consisting of multiple vehicle types. the curbside area or zone. Also see "Bypass vehicles." Operational characteristics--Traffic flow characteristics, Time path--A person's perceived time incurred while trav- including speed, density, vehicle mix, and volumes. eling along a defined path or route, including time in motion, delays caused by congestion, and waiting time. Passenger car equivalent (pce)--The number of passenger cars displaced by a single heavy vehicle of a particular type Traffic controls--Devices directing vehicular and pedestrian under specified roadway, traffic, and control conditions. traffic flows, particularly at conflict areas, including signals, signs, and pavement markings. Passenger load factor--A measure of available aircraft seats that are occupied. Transborder flight--As used in this Guide, scheduled flights between the United States and Canada whose passengers have Peak hour--The peak hour is the busiest hour of the year, typically been pre-cleared by border controls. month, or day. It is suggested that the "design hour," rather than the peak hour, be used for planning and evaluation of Transportation demand management (TDM)--The appli- airport roadways, and that the design hour be a typical busy cation of policies and strategies to reduce travel demand or hour on the peak day of the week during the peak month. redistribute this demand in space or time. Peak-hour factor--The relationship between the hourly traf- Trip generation rate--The number of vehicle or person trips fic volume in the peak hour and the maximum rate of flow generated by a household, zone, land use, or other facility within some portion of the hour. As used most commonly, generally during a daily or peak period. this factor refers to the ratio of the hourly volume to the max- Triple parking--A situation in which three or more adjacent imum 15-minute flow rate expanded to an hourly volume. vehicles are parallel parked or stopped along the curbside Performance capabilities--As used in this Guide, the capa- roadway. bilities of an individual vehicle or group of vehicles, includ- Weaving area--The roadway segment in which two or more ing acceleration, maneuverability, and turning radii. traffic streams traveling in the same general direction along a Poisson distribution--A discrete probability distribution significant length of roadway cross one another without the that expresses the probability of a number of events occurring aid of traffic control devices. in a fixed period of time. Weaving distance--The distance from a point on the merge Remote curbside--A curbside located outside of the immedi- gore at which the right edge of the freeway shoulder lane and ate area of the passenger terminal building, such as in a park- the left edge of the merging lane are 2 feet apart to a point on ing structure, surface lot, or multimodal facility. the diverge gore at which the edges are 12 feet apart. Rental car ready/return--The parking or storage area(s) to Weaving intensity factor--A measure of the influence of which rental car customers return rented vehicles or pick up weaving activity on the average speed of both weaving and rental vehicles. nonweaving vehicles. Signal phasing--The part of a traffic control signal time cycle Vehicle mix--The proportion of each type of vehicle (i.e., allocated to any traffic movement given the right of way. bus, car, van, truck) in a traffic stream. Skycap--A porter employed by an airline or airport operator Vehicle occupancy--The number of passengers (including to provide baggage drop service to passengers. the driver) in a vehicle. Steady-state performance--The traffic flow rates occurring Vehicle stall length--As used in this Guide, the length of curb on a roadway or intersection when the traffic stream is not space occupied by a stopped vehicle, including the distance disrupted or interrupted. required to maneuver into and out of the space.