Average Daily Traffic (ADT)
The volume during a given time period (in the whole days greater than one day but less than one year) divided by the number of days in that time period and expressed in terms of veh/day.
Average Annual Daily Traffic (AADT)
It is the total yearly volume divided by the number of days in a year.
Design Hourly Volume (DHV)
It is the economic hourly flow of future year, which is used for designing geometric features of roadway.
The vehicle whose weight, dimensions and operating characteristics are used to established the geometric standards of the highway
The design speed is defined as the “maximum safe speed that can be maintained over a specified section of highway when conditions are so favorable that the design features of highway govern
The capacity of a given section of roadway may defined as the maximum hourly rate at which vehicle can reasonably travel a point or uniform section of roadway during a given period under prevailing roadway, traffic and control conditions
Level of Service (LOS)
Level of service is a qualitative measure that describes operational condition within a traffic stream and their perception by road users.
Lane width usually vary from
A median is the section of a divided highway that separates the lanes in opposing directions
Right of Way
The right of way is the total land area acquired for the construction of the highway
Physical devices which is used to control and guide motorist, prevent vehicles from leaving the roadway and crossing into wrong side, facilitated drainage.
Median and roadside barrier, guardrails/ Guard post, Curbs and Gutters, Island/Channel, Sign, signal, light post
The maximum hourly rate of an approach at a signalized junction/ the maximum rate of discharge for a particular approach
Flow that is generated because of new or improved roadway facility
When demand is at or near or exceeds the roadway capacity and the average rate of flow remains almost constant with time.
When land changing opportunity decreases with increasing traffic volume and drivers are forced to follow slow leaders.
Passenger Car Equivalent (PCE)
It is the method of expressing various types of vehicles having different characteristics in a common equivalent unit. One car is considered as one unit.
In respect to its road occupancy and operational requirements each type of vehicle is equivalent to a number of passenger cars and this is called the Passenger Car Equivalent.
Amber period/Clearance time (a)
To allow vehicles to clear the junction (usually 3 seconds)
Inter-green period (I)
The time from the end of the green period of the phase losing right-of-way to the beginning of the green period
Optimum Cycle Length (Co)
The cycle time which gives the least average delay to all vehicles using the intersection
Lost Time (L)
The time which is effectively lost to traffic movement in a phase because of starting delays and the falling-off discharge rate during the amber period
Effective Green Time (G)
The time during the cycle when the traffic flows freely discharge through green aspect at the maximum rate
All red period
A red period between the amber and red-amber shown to all approaches in order to allow vehicles to clear the junction safely before starting the next phase
Instantaneous speed of a vehicle at a point
Average speed while in motion
Overall speed including stop
The highest overall speed
Free Flow Speed
When drivers face no restriction in driving and can maintain their desired speeds
The speed below 85% vehicle move (85th percentile speed)
The speed below 98% vehicle move (98th percentile speed)
The speed below 50% vehicle move (50th percentile speed)
Speed at the highest frequency
It is a range of speed (usually taken in 10 mph or 15 kmph increment)
Upper limit at 85th percentile speed
Lowe limit at 15th percentile speed