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Fatalities by VMT (vehicle miles traveled) is a unit for assessing road traffic fatalities. This metric is computed by dividing the fatalities by the estimated VMT. Usually, transport risk is computed by reference to the distance traveled by people, while for road traffic risk, only vehicle traveled distance is usually taken into account. [7]
Density (k) is defined as the number of vehicles per unit length of the roadway. In traffic flow, the two most important densities are the critical density (k c) and jam density (k j). The maximum density achievable under free flow is k c, while k j is the maximum density achieved under congestion. In general, jam density is five times the ...
In the study of traffic flow theory, the flow-density diagram is used to determine the traffic state of a roadway. Currently, there are two types of flow density graphs: parabolic and triangular. Academia views the triangular flow-density curve as more the accurate representation of real world events. The triangular curve consists of two vectors.
Level of service (LOS) is a qualitative measure used to relate the quality of motor vehicle traffic service. LOS is used to analyze roadways and intersections by categorizing traffic flow and assigning quality levels of traffic based on performance measure like vehicle speed, density, congestion, etc.
In free traffic flow, empirical data show a positive correlation between the flow rate (in vehicles per unit time) and vehicle density (in vehicles per unit distance). This relationship stops at the maximum free flow q max {\displaystyle q_{\max }} with a corresponding critical density k crit {\displaystyle k_{\text{crit}}} .
In transportation engineering, the K factor is defined as the proportion of annual average daily traffic occurring in an hour. [1] This factor is used for designing and analyzing the flow of traffic on highways. K factors must be calculated at a continuous count station, usually an "automatic traffic recorder", for a year before being determined.
Annual average weekday traffic (AAWT) is similar to AADT but only includes Monday to Friday data. Public holidays are often excluded from the AAWT calculation. Average summer daily traffic (abbreviated to ASDT) is a similar measure to the annual average daily traffic. Data collecting methods of the two are exactly the same, however the ASDT ...
Passenger car equivalent (PCE) or passenger car unit (PCU) is a metric used in transportation engineering to assess traffic-flow rate on a highway. [1]A passenger car equivalent is essentially the impact that a mode of transport has on traffic variables (such as headway, speed, density) compared to a single car.