transportation engineering Transportation engineering or transport engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation in order to provide for t ...

, the K factor is defined as the proportion of

annual average daily traffic Annual average daily traffic, abbreviated AADT, is a measure used primarily in transportation planning, transportation engineering and retail location selection. Traditionally, it is the total volume of vehicle traffic of a highway or road for ...

occurring in an hour. This factor is used for designing and analyzing the flow of traffic on

highways A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-access ...

. K factors must be calculated at a continuous count station, usually an "automatic traffic recorder", for a year before being determined. Usually this number is the proportion of "annual average daily traffic" (AADT) occurring at the 30th-highest hour of traffic density from the year's-worth of data. This 30th-highest hour of traffic is also known as "K30" or the "Design Hour Factor". This factor improves

traffic forecasting Transportation forecasting is the attempt of estimating the number of vehicles or people that will use a specific transportation facility in the future. For instance, a forecast may estimate the number of vehicles on a planned road or bridge, the r ...

, which in turn improves the ability of designers and engineers to plan for efficiency and serve the needs of this particular set of traffic. Such forecasting includes the selection of pavement and inclusion of different geometric aspects of highway design, as well as the effects of lane closures and necessity of traffic lights. Engineers have reached consensus on identify K30 as reaching a reasonable peak of activity before high outliers of traffic volume are used as determinative of overall patterns. The K factor has three general characteristics: * K generally decreases as AADT increases. * K generally decreases as development density increases. * K is generally highest near recreational facilities, next highest in

rural In general, a rural area or a countryside is a geographic area that is located outside towns and cities. Typical rural areas have a low population density and small settlements. Agricultural areas and areas with forestry typically are descri ...

and

suburban area A suburb (more broadly suburban area) is an area within a metropolitan area, which may include commercial and mixed-use, that is primarily a residential area. A suburb can exist either as part of a larger city/urban area or as a separa ...

s, and lowest in

urban area An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, ...

s. Another notable proportions of K is the measure of K100 (the proportion of AADT occurring during the 100th highest hour of the design year). This proportion is also known as the Planning Analysis Hour Factor.

Calculation

The calculation for the K factor is given by the formula in which DHV is the "Design Hourly Volume," the 30th highest hourly traffic volume (in both directions) in the year in which data was collected, by vehicles per hour.

Usage

The use of the K30 standard is mandated for the Highway Performance Monitoring System's comparisons of congestion. The K Factor also helps calculate the peak-to-daily ratio of traffic. K30 helps maintain a healthy

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...

to capacity ratio.

References

Transportation engineering {{transport-stub