Traffic Bowl Vocab

headway

time difference between one point on front vehicle and same point on rear vehicle

gap

time difference between rear of leading vehicle and front of following vehicle

clearance: distance between rear of leading vehicle and front of following vehicle

flow rate

number of vehicles/time

density

number of vehicles/length

time

mean speed

space

mean speed

fundamental law

q = k*v

occupancy

the fraction of time that a detector is covered by a vehicle

capacity

volume of vehicles at maximum flow rate

greenshields

speed vs. density

demand

number of vehicles that desire to travel past a point during a time period

saturation flow rate

number of vehicles per hour that could cross the line if the signal

remained green all of the time

phase

green interval plus change and clearance intervals

actuated signal

initiation of a change in traffic signal operation when vehicles arrive at intersection

arterial highway

a highway primarily used by thru traffic on a continuous route

collector

connects local roads to arterials

CBD

central business district

NEMA

National Electrical manufacturer association

diamond interchange

is a common type of road junction, used where a freeway crosses a minor road.

LOS

level of service

approach

all lanes moving toward an intersection

traffic calming: is about preserving the function of local street. Goal is to reduce traffic volume, reduce traffic speed, reduce acident

ETC

Electronic Toll Collection

Expressway

divided highway with partial control of access

Grade Crossing

where a highway and railroad cross at same level

HOV

high occupancy vehicle

dropped lane

a thru lane that becomes a mandatory turn lane or exit lane

interchange

interconnecting roadways between two or more highways that don’t intersect at grade

Dual

Arrow Signal Section—a type of signal section designed to include both a yellow arrow and a green arrow.

Edge Line Markings—white or yellow pavement marking lines that delineate the right or left

edge(s) of a traveled way.

interval

part of a signal cycle where signal indications do not change

median

area between two roadways on a divided highway

neutral area

paved area between lines separating entrance or exit ramp

occupant

a person driving or riding in a vehicle

platoon

group of vehicles traveling as a group

right

of

design speed

speed used to determine various geometric design features of a roadway

delineator

vertical objects that direct traffic

auxiliary lane

roadway for weaving, truck climbing or speed change

gore

area immediately beyond the divergence of two roadbeds bounded by edges of those roadbeds

weaving section

length of roadway designed to accommodate two traffic streams merging and dividing within a short distance

freeway

a divided highway with full control of access.

guide sign

a sign that shows route designations, destinations, directions, distances, services,

points of interest, or other geographical, recreational, or cultural information.

trip generation

predicts # of trips originating or destined for a traffic analysis zone

trip distribution

matches tripmakers’ origin to each destination

mode choice

determines what mode of tranpso will be used

route assignment

selection of routes between origins and destinations

traffic analysis zone

unit of geography used in transportation modeling

AADT

annual average daily traffic

FAA

federal aviation administration