You need to upgrade your Flash Player
Download the most recent Flash plugin here.


The portion of a truss span between adjacent points of intersection of bridge web and chord members.
Comparable transportation service required by the Americans with Disabilities Act (ADA) of 1990 for individuals with disabilities who are unable to use fixed-route transportation systems.
parclo loop ramp
A (partial cloverleaf) interchange with loops in advance of the minor road with direction of travel on the freeway; and in the same interchange area, an interchange with loops beyond the minor road.
A mode of travel, usually associated with movements between work and home that involve use of a private auto on one portion of the trip and a transit vehicle (i.e., a bus or a light-rail vehicle) on another portion of the trip.
partial interchange lighting (PIL)
Lighting on an interchange that consists of a few luminaries located in the general areas where entrance and exit ramps connect with the through traffic lanes of a freeway (between the entry gore and the end of the acceleration ramp or exit gore and the beginning of the deceleration ramp).
passenger facility charge
A tax authorized by Congress, approved by the Federal Aviation Administration, assessed by airports, and collected by airlines as an add-on to the passenger airfare; it is designated to help pay for airport improvements that enhance safety and capacity and is not revenue for airlines.
passenger miles
The total number of miles traveled by passengers on transit or railroad vehicles.
Unit of measure that is a product of average trip length multiplied by number of passengers; statistics for transportation safety, for example, are cited on the basis of passenger miles.
passive warning device
Signs or markers used at all highway-rail grade crossings.
Pavement Condition Index (PCI)
A 0-100 rating representing the condition of state highway pavements (0 worst 100 best); PCI is a measure of pavement condition only and does not consider geometrics, safety or congestion; the index is used as a network-level performance measure and as one of many tools to identify pavement improvement needs.
peak intensity
The maximum strength of a traffic signal maintained through a defined viewing angle; measured in candelas.
A person on foot, in a wheelchair or walking a bicycle.
pedestrian control device
A special type of device (including pedestrian signal indications and sign panels) intended for the exclusive purpose of controlling pedestrian traffic in crosswalks.
pedestrian facility
A facility provided for the benefit of pedestrian travel, including walkways, crosswalks, signs, signals, illumination and benches.
perception-reaction time (PRT)
The interval between a driver's detection of a target stimulus or event and the initiation of a vehicle control movement in response to the stimulus or event.
A vertical support or substructure unit that supports the spans of a multispan superstructure at an intermediate location between its abutments.
A shaft-like linear member that carries loads through weak layers of soil to those capable of supporting such loads.
pile bent
A row of driven or placed piles with a pile cap to hold them in their correct positions; see bent.
plate girder
A large solid web plate with flange plates attached to the web plate by flange angles or fillet welds.
The clear, unobstructed space of a bridge forming the entrance to the structure.
positive offset
A term used to describe the alignment of opposing left-turn lanes at an intersection; this geometry exists when the left boundary of one left-turn lane, when extended across the intersection, falls to the right of the right boundary of the opposite left-turn lane.
posted speed
This term refers to the posted speed limit on a given street or the legal speed limit as defined.
post-mounted delineators (PMDs)
Retroreflective devices located serially at the side of a roadway to indicate alignment; each delineator consists of a flat reflecting surface, typically a vertical rectangle, mounted on a supporting post.
preliminary design
An engineering design that specifies in detail the location and alignment of a planned transportation facility or improvement.
Primary Highway System
Highways that have been functionally classified by the Iowa Department of Transportation as either principal or minor arterials, and that have been selected by the Iowa Transportation Commission to be placed on the Primary Highway System.
A general term to refer to a series of activities carried out by planners, including data assessment, appraisal of identified planning needs, and consideration of available or anticipated fiscal resources to result in the drawing up, scheduling, and planning of a list of identified transportation improvements for a given period of time.
public hearing
A NEPA required meeting designed to afford the public the latest project information and the opportunity to express support of or opposition to a transportation project in a forum at which a verbatim record (transcript) of the proceedings is kept.
public meeting
An announced meeting conducted by transportation officials designed to facilitate participation in the decision-making process and to assist the public in gaining an informed view of a proposed project at any level of the transportation project development process; also, such a gathering may be referred to as a public information meeting.
public service announcement (PSA)
Television and/or radio messages.
public transportation
Services provided for the public on a regular basis by vehicles such as a bus or rail on public ways, using specified routes and schedules; usually on a fare-paying basis; also includes nonscheduled, on-demand transit services.