Glossary terms
- Active Traffic Management (ATM)
- The ability to dynamically and proactively manage recurrent and nonrecurrent congestion on an entire facility based on prevailing traffic conditions.
- Active Transportation and Demand Management (ATDM)
- The dynamic management, control, and influence of travel demand, traffic demand, and traffic flow of transportation facilities.
- ATDM
- Abbreviation for Active Transportation and Demand Management
- ATM
- Abbreviation for Active Traffic Management
b
- Benefit/Cost Analysis
- An analysis comparing all measureable consequences of a project by attributing them a monetary value.
- Bus-bypass Shoulder
- A shoulder exclusively accessible to transit busses either on a part-time or full-time basis.
c
- Capacity
- The theoretical maximum amount of vehicles crossing a section of the highway in an hour.
- Changeable Message Sign
- See Dynamic Message Sign.
- CMS
- Abbreviation for changeable message sign.
- Cost
- The resources used to produce a good or service.
d
- Delay
- The increased travel time experienced due to circumstances that impede a desirable movement of traffic.
- DMS
- Abbreviation for dynamic message sign.
- Dynamic Merge Control
- An ATM measure consisting of allocating lane access on the general purpose lanes and ramps based on the traffic already present on the highway and merging traffic in order to provide priority to the facility with the higher volume and give a lane drop to the lesser volume roadway or approach.
- Dynamic Message Sign
- A permanently installed or portable electronic traffic sign used on roadways to give travelers information about roadway conditions. Often abbreviated as DMS.
- Dynamic Pavement Marking
- An in-pavement traffic control device that can be activated to show alternative lane delineation.
- Dynamic Rerouting
- An ATM measure consisting of providing route information on overhead sign gantries along a roadway in response to recurrent and non-recurrent congestion.
- Dynamic Speed Limits
- See Variable Speed Limits
- Dynamic Truck Restrictions
- An ATM measure that restricts trucks from using specific lanes on a facility, limiting their operating speed, and/or prohibiting their use of an entire facility during specific periods of the day.
e
- Emergency Refuge Area
- The free space available beyond the shoulder to safely harbor vehicles in distress.
- Enforcement
- Function of maintaining the rules and regulations of a preferential treatment to maintain the integrity.
f
- Feasibility Study
- A study meant to assess whether a project is worth pursuing.
- FHWA
- Federal Highway Administration.
- Flow Profile
- A figure showing the variation of traffic flow as a function of the time of the day.
g
- General-Purpose Lanes
- Lanes on a freeway or expressway which are open to all motor vehicles.
h
- Hard Shoulder Running
- See Temporary Shoulder Use.
- Highways Agency
- Executive part of the Department of Transport responsible for operating, maintaining and improving the strategic road network in England on behalf of the Secretary of State for Transport.
i
- Interchange
- The system of grade-separated ramps connecting two or more roadways.
j
- Junction Control
- See Dynamic Merge Control.
l
- Lane Control Sign
- A DMS placed on top of each lane on overhead gantry with the ability to show a green arrow (open lane), a yellow arrow (closing lane) or a red cross (closed lane).
- Level of Service (LOS)
- A qualitative measure that describes the operational conditions of a roadway or intersection.
- Line Control
- See Speed Harmonization.
m
- Main Lane
- A general purpose lane on a freeway that is open to all motor vehicles.
- Motorway Incident Detection and Automatic Signaling (MIDAS)
- A British incident detection and management program.
- Motorway Traffic Management (MTM)
- A Dutch incident detection and management program.
o
- Obstacle
- Any object or situation that might hinder the ability to use the roadway or shoulder safely.
p
- Peak Hour
- The hour in which the maximum demand occurs on a facility.
- Peak Period
- The period during which the highest volumes are observed daily on a regular basis.
q
- Quality of Flow
- See Level of Service (LOS)
- Queue
- A line of vehicles on a transportation facility.
- Queue Warning
- An ATM measure consisting of the display of warning signs and flashing lights along a roadway to alert drivers that congestion and queues are ahead.
r
- Raised Pavement Markers
- Traffic control devices, usually retroreflective, embedded in the pavement and meant to delineate lanes in addition to striping.
- Ramp Metering
- The procedures used to reduce congestion by managing vehicle flow from local-access on-ramps using a traffic signal at the entrance ramp that allows vehicles to enter the freeway at predetermined intervals.
- Rijkswaterstaat
- Dutch ministry of transports and water management.
- Rotating Sign
- Sign that can show two or more messages by rotation of the panel is composed of.
s
- Shockwave
- An imaginary line delineating a disruption in vehicle speeds.
- Speed Harmonization
- An ATM measure consisting of using an expert system to monitor data coming from the field-deployed sensors on a roadway and automatically adjusting speed limits when congestion thresholds are exceeded and congestion and queue formation are impending; Sign gantries that span the facility provide speed limits and additional information depending on the roadway conditions.
t
- Temporary Shoulder Use
- An ATM measure consisting of opening a shoulder to traffic on a temporary basis to address capacity bottlenecks on the freeway network during times of congestion and reduced travel speeds.
- Traffic Management Center
- A surveillance and control center for the road network in the area.
- Traffic Volume
- The amount of vehicles crossing a section of a road in a hour time.
- Travel Time
- The length of time it takes to travel between two points.
- Travel Time Reliability (TTR)
- A term referring to the variability in travel time that can be expected using different facilities.
v
- Variable Message Sign (VMS)
- See Dynamic Message Sign (DMS)
- Variable Speed Limits (VSL)
- Speed limits that change based on road, traffic, and weather conditions.
- Vehicle Miles Traveled (VMT)
- The total distance traveled in miles by all motor vehicles of a specific group in a given area at a given time.
w
- Weaving Lane
- A lane used for both merging on the highway and exiting the highway.
a