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telecommuting
The practice of allowing selected employees to work at home or at a remote site rather than the traditional work site to eliminate the commute trip.
temporary pavement marking treatment
This treatment primarily involves the application of paint or tape striping and has been shown to be important for effective vehicle guidance at highway work sites.
tension
A force that pulls or stretches.
through freight train
An express freight train between major terminals.
tie
A member carrying tension, such as a railroad or wire tie.
timetable
The authority for the movement of regular trains subject to the rules; it may contain classified schedules and include special instructions.
T-intersection
An intersection that involves three legs, where one leg is perpendicular to the other two legs; there are several types of this intersection, such as plain, with turning lanes and channelized.
torsion
A twisting force or action.
tower
The vertical structure in a suspension bridge (or cable-stayed bridge) that holds up the suspension cables.
track car
Equipment, not classified as an engine, which is operated on railroad track for inspection or maintenance; it may not shunt track circuits or operate signals and will be governed by rules and special instructions for trains other than passenger trains.
trackage rights
Rights obtained by one railroad to operate its trains over another railroad's tracks.
traffic
The number of motor vehicles in a given location at a given point in time.
traffic calming
A transportation system management technique that aims to prevent inappropriate through-traffic and reduce motor vehicle travel speed on a particular roadway; traditionally, this technique has been applied to local residential streets and collectors, and may include speed bumps, curb extensions, planted median strips or rounded and narrowed travel lanes.
traffic circle
An intersection where traffic moves around a circular center island; some traffic circles have traffic signals, also called a roundabout.
traffic control device
The prime, and often the only, means of communicating with the driving public; these devices (e.g., signs, markings, signals, islands) must be used discriminately, uniformly and effectively to assure correct driver interpretation and response.
traffic count
A tabulation of the number of vehicles passing a certain point over a specified time period; this is often a 12- or 24-hour period.
trainload
The number of occupants or the amount of material that a passenger or freight train can hold.
trainmaster
A railroad employee who is in charge of a railway yard.
train-mile
The movement of a train a distance of one mile; mileage measurement is not increased because of the presence of multiple locomotives in the train.
transit route
A designated, specified path assigned to a transit vehicle.
transit stop
An area where passengers wait, board and transfer between transit vehicles.
transload
A transload facility with full intermodal capabilities is a place where rail or barge freight is combined to take advantage of multiple modes of transportation.
transportation analysis
Corridor analysis is a detailed analysis of a roadway performed for the purpose of obtaining the most accurate projected traffic volumes. The analysis takes into account existing traffic volumes, projected growth, and major traffic generating locations. A corridor analysis will yield projected traffic volumes for every movement allowed on a facility including main lane, ramp, frontage road, and turning volumes.

Design analysis is an analysis is used to determine the number of lanes required to deliver a specific level of service based on a forecast demand volume and given geometric design standards.

Operational analysis is an analytic evaluation of operations on an existing highway segment. The same type of analysis may be applied to evaluate probable operating conditions on a future facility. All traffic and roadway conditions must be specified, as well as traffic volumes. The typical situations which can be resolved through this type of analysis include the comparison of flow conditions for different volume levels and number of lanes. This type of analysis might also be used to establish the impacts of a change in the number of access points along a given section of multilane highway. Another typical application of an operational analysis might be to develop several alternative packages that would be used to improve the level of service or travel speed along a multilane highway.

Planning analysis is similar to design analysis in that the number of lanes needed for a level of service is determined. However, the planning analysis requires much less input of detail, and it uses a very rough estimate for directional design hourly volume and using the design procedures.
transportation management associations (TMA)
This term refers to nonprofit coalitions of local businesses and/or public agencies dedicated to reducing traffic congestion and pollution and improving commuting options for employees. As defined in federal regulations, this term refers to "an urbanized area with population of 200,000 or greater" and "applies to the entire metropolitan planning area." All locations must meet certain standards, and nonattainment. TMAs must meet additional planning requirements.
trestle
A bridge structure consisting of spans supported upon frame bents.
tri-level
Enclosed rail freight car for carrying three levels of automobiles.
truck terminal
A facility that serves as a primary gateway for commodities entering or leaving the metropolitan area.
trumpet interchange
A three-legged interchange where a connecting highway terminates and where only a small amount of traffic moves between the terminating highway and one of the two legs of the freeway; the trumpet is laid out so that this minor traffic moves via a 200-degree loop.
truss
A rigid, jointed structure made up of individual straight pieces arranged and connected, usually in a triangular pattern, so as to support longer bridge spans.
truss bridge
A bridge having a pair of trusses for the superstructure.
trust funds
Funds collected and used by the federal government for carrying out specific purposes and programs according to terms of a trust agreement or statute, such as the Social Security and highway trust funds; trust funds are administered by the government in a fiduciary capacity and are not available for the general purposes of the government.
tunnel
An underground passage open to daylight at both ends.
two-quadrant cloverleaf interchange
A type of partial cloverleaf where most traffic leaving one highway turns to the same leg of the intersecting highway.