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Glossary of Terms and Diagrams

This Glossary of terms and associated diagrams is intended to provide a common definition and form a mutual understanding for all users of this report:

AASHTO – American Association of State Highway and Transportation Officials.

ACM – Automatic Coin Machine – Unattended toll collection equipment installed on a toll island consisting of a coin hopper to collect and funnel coins or tokens, a coin processor for identifying and recording coin denominations, and automatic locking coin vaults for storing coins or tokens.

ADA – Americans with Disabilities Act.

Approach Queue Zone – A rectangular shaped area extending longitudinally from the far approach edge of the toll islands to a distance in front of the toll plaza where one or both of the outside edges of the zone begin to taper toward the center of the plaza and transversely to encompass all toll plaza lanes (excluding express lanes). This area is intended to provide space for vehicle queues without blocking approaching vehicle access to any of the open toll lanes.

Approach Transition Zone – The area upstream of the toll plaza where the roadway widens from the typical roadway section in advance of the toll plaza to the width of the approach queue zone.

ATIM – An automatic ticket issuing machine or automatic ticket dispenser (ATD) that is used to dispatch a ticket coded with time, date, a default vehicle class and entry location information used to determine the toll due when exiting the facility. A loop detector activation is commonly used to signal the ATIM or ATD to automatically issue a ticket.

Barrier Gate – An automatic gate consisting of a breakaway gate arm, motor assembly and housing installed at the departure end of a toll island. A barrier gate is used to reduce violations and speed through a toll lane. Barrier gates installed in both attended and unattended lanes commonly includes a remote control capability to raise the gate for patrons with insufficient funds.

Beacon - A traffic signal, commonly consisting of one signal head that operates in a flashing mode. It is used to draw attention to a sign, obstruction, or hazardous condition.

Branch Toll Lanes – Channelized toll lanes located either in advance of or after a toll plaza that are used to increase toll plaza capacity within existing right-of-way constraints. A single main toll plaza lane is effectively converted to multiple lanes using the same modes of collection available in the main toll plaza by shifting the collection points either upstream or downstream.

Bypass Lanes – A lane that circumvents the toll plaza that is typically used by special permit and oversized vehicles. When this lane is routed around the administration building, it is also used for deliveries to the toll plaza and building. The lane may also be used for an oversized vehicle to turnaround. Gates, cameras and other security control features are commonly used to restrict access to these lanes.

Canopy – A structure consisting of a roof and support columns used to protect toll attendants and customers from precipitation. This structure is commonly used to support overhead signs and signals along with ETC and violation enforcement equipment.

Cars-only ETC Lane - A dedicated ETC lane allowing only cars equipped with a valid transponder to use the lane to record a toll transaction.

CMS - Changeable Message Sign – A traffic control device capable of changing state by displaying one or more messages. These signs support a blank mode, multiple messages alternately displayed, and more than one message with one message continuously displayed. A CMS displays pertinent traffic operational, regulatory, warning, and guidance information. These signs are capable of being changed manually, by remote control, or by automatic controls. Toll plazas typically use a single or multi-line electronic sign mounted overhead to display the operating status and toll collection mode of a single or group of toll lanes located ahead or directly below the CMS. LEDs and illuminated fiber strands are the most common technologies used to display messages. The CMS can be mounted to a canopy, gantry, bridge, or cantilever structure and requires provisions for accessing the signs internal components from the front, rear or interior of the sign.

Crash Block – Formed reinforced or mass concrete placed in front of a tollbooth to protect the tollbooth and attendant from direct vehicle collisions. A crash block can be placed monolithic with a toll island or separately after placement of the toll island. The height of the crash block is limited by the tollbooth window height and the width is normally limited by the width of the toll island minus a setback to minimize damage to passing vehicles. Single crash blocks are commonly used in conjunction with ramparts and dual crash blocks are commonly used on longer length toll islands.

Crash Cushion – See “Impact Attenuator”.

Dedicated ETC Lane – A toll lane within a conventional toll plaza that is dedicated to an ETC method of payment, thereby limiting use of the lane to vehicles having a valid transponder. Except for maintenance servicing, this lane is typically open 24 hours per day. Three common variations of these lanes are mixed-use, cars-only, and trucks-only. These lanes are normally located to the left of a directional toll plaza, but may be located in the center or on the right side because of vehicles entering the plaza from two directions, to accommodate reversible lanes, reduce implementation cost by converting only ACM lanes and low expected usage.

Delineator – A retro-reflective device mounted on the roadway surface or at the side of the roadway, typically in a series, to indicate alignment of the roadway and to channelize vehicles to form queues and/or prevent crossing into an adjacent lane or accessway.

Departure Recovery Zone – A rectangular shaped area extending longitudinally from the far departure edge of the toll plaza islands to a distance downstream of the toll plaza where one or both of the outside edges of the zone begin to taper toward the center of the plaza and transversely to encompass all toll plaza lanes (excluding express lanes). This area allows motorists to orient themselves to the approaching tapers and the possible need to merge to the left or right after exiting the toll lane.

Departure Transition Zone - The area immediately downstream of the departure recovery zone of the toll plaza where the width of the roadway narrows to the width of the typical roadway section.

Diffusers – Slightly angled horizontal slats mounted in front of a high intensity light to diffuse a light beam used to enhance the capture of a vehicle license plate. The slats are commonly welded to a four-sided box. Diffusers are used to mitigate impairment of a driver’s visions when viewed directly or from a rear-view mirror.

DOT – Department of Transportation

ETC – Electronic Toll Collection – A subsystem capable of electronically charging a toll to an established customer account by reading a number matched to an account and encoded on a transponder that is mounted inside or to the bumper of a vehicle. Lane level equipment consists of an overhead mounted antenna, a transceiver/modulator for processing RF signals, a reader/controller for both verification processing and data storing, and a vehicle mounted transponder.

Express Lanes – Roadway lanes effectively equivalent in design to the approach and departure roadway sections with the exception of roadside barrier installed to minimize the severity of collisions with a vertical support of a bridge, gantry or cantilever structure used to support toll collection, vehicle classification and violation enforcement equipment. Tolls are predominately charged using an electronic process for vehicles having a valid transponder and to a much lesser extent by capturing vehicle license plates and assessing a toll to the registered vehicle owner. The primary method of violation enforcement in these lanes is license plate capture using overhead or side mounted cameras. All toll and violation transactions are recorded while vehicles are traveling through the lanes at prevailing highway speeds.

Green Book – A Policy on Geometric Design of Highways and Streets published by American Association of State Highway and Transportation Officials. This document provides design guidance based on established practices and forms a comprehensive reference manual for assistance in administrative, planning and educational efforts pertaining to design formulation.

High Mast Lighting – Multiple luminaries typically installed in a ring configuration at the top of a pole at least 55 feet tall. The interior of the pole commonly houses components of a lowering mechanism used to drop the ring of luminaries to an adjustable distance above ground level for maintenance.

Impact Attenuator – An energy absorbing crash cushion designed to decrease the momentum of a vehicle traveling at a particular speed and reducing the severity of property damage and injuries to the driver of the vehicle and the toll attendant operating from inside a downstream toll booth. The back end of the impact attenuator is anchored a concrete back-up block for stability and to minimize the potential of the vehicle colliding with a toll booth or equipment.

ITE – Institute of Transportation Engineers - An international association of transportation professionals responsible for planning, designing, implementing, operating, and maintaining the surface and ground transportation systems of the world. ITE provides for the professional development of members and others in meeting society’s needs for safe, efficient and environmentally compatible transportation.

ITS – Island Traffic Signal – Two or three vertically stacked standard traffic signal heads mounted to the top of a stanchion or post. The ITS is mounted at the downstream end of the toll island. Red and green signal heads convey the same meaning as traffic signals installed at intersection, while a yellow signal head is commonly used to indicate a low ETC account balance. The ITS may also include a combination alarm and light mounted to the top of the assembly that is activated by the System whenever a vehicle exits the lane without recording a paid transaction.

Lane Use Signal – A device commonly mounted over the center of a toll lane and used to display an open or closed lane operating status. The most common signal types installed in toll plazas use a red “X” for closed and green “↓” for open. These symbols are primarily formed from LEDs or illuminated fiber strands, either installed in an off-the-shelf environmental enclosure or part of a multi-line changeable message sign. Horizontally placed red and green traffic signal heads are also used to display lane status.

Light Curtain – An array of photoelectric sensors that emit and receive sequenced and modulated light beams that are used to detect the presence and/or define a profile of a vehicle. A controller is used to receive an output signal from each receiver, apply logic for reliable detection or profiling under varying environmental conditions, and communicate output and operational messages to an interconnected processor (e.g. lane controller).

Manual Toll Collection - A method of toll collection involving a toll attendant classifying vehicles, collecting cash or swiping magnetic cards, providing change and receipts, and collecting vehicle information for instances of unpaid tolls.

Mixed-Use ETC Lane – A dedicated ETC lane allowing both cars and trucks equipped with a valid transponder to use the lane to record a toll transaction.

ML Plaza – Mainline Toll Plaza –A toll plaza located on the mainline of a tollway which effectively creates a barrier to prevailing traffic flow, with the exception of express lanes, and to a lesser extent, dedicated lanes.

Moveable Barrier – A series of linked concrete or sand-filled barriers used to separate opposing flows of traffic and capable of being moved by automated, continuous-flow, mechanical means to change traffic patterns.

MUTCD – Manual on Uniform Traffic Control Devices

Photoelectric Beam – An electrical device that is used to detect the presence of a vehicle at the location of the barrier gate arm. Toll facility implementations commonly consist of either emitter and receiver self-contained units or a self-contained emitter/receiver and reflector. The receiver sends an analog or digital output signal when changes in light intensity are detected.

PTD – Patron Toll Display - A relatively small electronic sign installed downstream of a toll booth or ACM to display toll due and toll paid messages and amounts for a particular vehicle class. A flip disc matrix consisting of movable discs coated with fluorescent dots is the most commonly used sign display technology.

Queue – A stacking of vehicles waiting to be serviced and/or processed by a toll attendant, ACM/ATIM, or ETC equipment.

Rampart – Sloped reinforced or mass concrete on the approach of the toll island intended to redirect an errant vehicle. The sloped concrete rises toward the booth and often connects to a crash block. The rampart may have rounded or approximately square edges.

RF – Radio Frequency – An electromagnetic wave frequency intermediate between audio frequencies and infrared frequencies, used especially in radio and television transmission as well as for transmission of information between a vehicle-mounted transponder and an overhead antenna.

Superelevation – An increase in the normal roadway cross slope or transitional removal of adverse crown or cross slope to flat before gradually increasing the roadway slope or tilting the roadway surface to partially counterbalance the centripetal force (i.e., lateral acceleration) on a vehicle that is negotiating a horizontal curve. The process is reversed upon exiting the curve.

Superelevation Rate – The rate of rise in cross section of the finished surface of a roadway on a curve, measured from the lowest or inside edge to the highest of outside edge.

Taper Rate – The transverse distance a roadway or pavement marking edge moves over a longitudinal length, as a ratio or a percent when multiplied by 100.

Tapered Chevron –White pavement markings of varying lengths that slope down at a 45 degree angle on both sides from a projected centerline of the obstruction (e.g. impact attenuator, toll island) to intersect a tapered white channelizing line. The total width at the approach end of the obstruction shall equal the width of the obstruction plus 1 to 2 feet on each side.

Throughput Volume – The number of vehicles passing through a toll lane or toll plaza in one direction over a one-hour or other defined time period.

Toll Collection Equipment - Equipment and devices used to detect vehicle presence, length, height and number of axles for the purpose of classifying vehicles, to collect cash/script or account ID numbers, process transactions, and to display fares, messages and indications to exit the lane.

Toll Facility – A road, bridge or tunnel for which travelers pay a specified toll for a particular class of vehicle to travel on, over, or through, respectively, the transportation facility.

Toll Island – A raised island or platform constructed with concrete that protects a toll booth, ACM, ATIM and other toll collection and violation enforcement equipment from damage caused by passing vehicles and to provide a sound foundation for securely mounting these items. Formed mass concrete is commonly placed at the approach end of the island to provide additional protection from errant vehicles.

Tolling Point – The location along a roadway lane where either a toll is charged to an established account using an electronic process for vehicles having a valid transponder or by capturing the vehicle’s license plate and assessing a toll to the registered vehicle owner.

Toll Schedule Sign – A sign that displays vehicle class and associated toll collected at a toll plaza. This sign is typically located on the right roadside, a short distance in advance of the plaza toll islands.

Truck-only ETC Lane - A dedicated ETC lane allowing only trucks equipped with a valid transponder to use the lane to record a toll transaction.

Figures 1-3 on the following pages are diagrams of toll plaza designs for reference purposes while reading this Report.

Figure 1 shows a plan view of a Manual Lane and a dedicated ETC Lane with associated glossary terms labeled on the diagram.

Figure 1 Manual Lane and Dedicated ETC Lane

Figure 2 presents a similar diagram for an ACM/ATIM Lane.

Figure 2 ACM/ATIM Lane

Figure 3 shows a plan view and a transverse centerline cross section of a typical mainline toll plaza with adjacent express lanes, including some of the geometric design features addressed in this report.

Figure 3 Mainline Toll Plaza with Adjacent Express Lane.


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