Level of Service (LOS) is a classification system which uses the letters A, B, C, D, E, and F to describe the quality of the mobility our transportation system provides for automobile traffic, pedestrians, bicyclists, and transit. LOS A represents the highest level of mobility, while LOS F represents the worst. The Florida DOT Quality/Level of Service Handbook uses the graphic shown in this PDF to visually depict LOS A - F for various modes of travel. LOS is closely related to the concept of capacity, which measures the quantity of traffic moving across a given point.
Measuring LOS is a complex process, particularly for multi-modal facilities due to the interaction between modes. This guide does not intend to provide instructions on how to complete the wide array of detailed calculations required to determine LOS. There are several "state-of-the-practice" resources that go into those details:
Pedestrians
Pedestrian LOS is determined by the following factors:
In areas with a significant pedestrian presence, actual pedestrian counts should also be considered.
TRB's Highway Capacity Manual provides a precedent for this approach. A variety of data is gathered for these four variables and used in a set of mathematical equations to obtain a score, which is then translated to a corresponding LOS.
Transit
LOS for Transit is primarily determined by frequency of service, as shown in the figure at right. As future MetroLink expansion considers on-street services, street car/trolley LOS will also be an important consideration. Quality and level of service for these modes also considers the type of shelters and stations provided at stops along the various routes.
Bicycles
Five key variables, listed below in order of importance, are used to determine bicycle LOS:
Like the Pedestrian LOS Model, a variety of data is gathered for these five variables and used in a set of mathematical equations to obtain a score, which is then translated to a corresponding LOS. It is important to note that the Bicycle LOS Model applies to on-street facilities, and not pathways or sidewalks.
The Bicycle Compatibility Index (BCI) is another model that was developed to predict the overall comfort experienced by a bicyclist on a given facility. The comfort level ranges from 1 to 6, with 1 being the most compatible rating and 6 being the least/worst. The index is based on qualitative comfort measures. See the BCI summary PDF and related links for more information.
Vehicles
For arterial streets and vehicular LOS specifically, areas are of interest are divided into two categories:
Planners and designers often refer to the "design year" when considering improvements for a vehicular street. The design year represents the planning horizon for the facility. For example, reconstruction of Manchester Road today would require the examination of some point in the future to determine the types of factors that must be considered in planning and designing improvements that will serve the future needs of the facility. Planners and designers will often examine the anticipated LOS for the design year of a facility in an effort to make sound decisions about current improvement recommendations.
Future traffic estimates, land use and development projections, population growth, and a variety of other factors all go into the determination of how much travel demand a facility is expected to serve at some point in the future. These projections are estimates based on assumptions of how development will affect future traffic. They are meant only to give an approximation of what the future condition might look like. They should be one of many factors to consider when planning and designing great streets.
It is not uncommon for planners and designers to establish a target for future LOS performance. The Missouri Practical Design Guide suggests that LOS E be the target for vehicular capacity in the design year for the urban/suburban place types considered in this guide. This is a target, it is not a mandate. The nature of the streets that we are concerned with will inevitably present situations where it is not possible to obtain LOS E. In that type of situation, a choice must be made: add capacity to the facility to achieve LOS E; or accept something worse than LOS E because the impacts associated with achieving LOS E would be too great and counter to the vision for the place. In the end, it is a choice that planners, designers, and local leaders must make.
Efforts to improve LOS for one mode may impact the LOS of other modes negatively. Ultimately, it is the type of place and its modal characteristics that determine the outcome of the competing LOS interests. Where pedestrian mobility is a priority, such as within a downtown area, the LOS for pedestrians, bicycles and transit should be prioritized over that for automobiles.
Along highways and rural routes, the LOS for cars will be a priority and along urban arterials, where the quality and safety of travel for many modes is necessary, the LOS for all modes must be carefully balanced. The solution for any place must reflect the vision and goals for that place, as determined collaboratively by the stakeholders. Long-term plan resolution is vital to the successful development of the ultimate vision.
Characteristics affecting LOS in Mixed Use Districts:
Although the needs of motor vehicle traffic should certainly be considered, LOS for pedestrians and transit must often take priority along downtown main street corridors. To accommodate and encourage a significant pedestrian presence, planners, designers, and local leaders should aim to:
Mixed-use districts are often popular bicycling corridors due to the lower motor vehicle travel speeds and more frequent transit service (some commuters may combine bicycling and transit use). The following measures can be taken to improve the bicycle LOS on mixed-use streets:
Despite the importance of providing a pedestrian- and transit-friendly environment in mixed use districts, it is still critical to maintain an adequate LOS for motor vehicle travel. Although these corridors should be great places for pedestrians, many visitors travel to mixed use districts via automobile; therefore, adequate vehicle capacity (and parking) in these areas is good for businesses and the overall vitality of the district.
Manageable levels of congestion in the form of slower travel speeds and longer delays at intersections can actually be beneficial in mixed use districts, because:
Mixed use districts should prioritize access and focus less on mobility. Because slower speeds are desirable along mixed use corridors, the LOS measures of average travel speed and delay can be applied with more flexibility.
Roundabouts can be an effective tool for reducing intersection delay in low-speed mixed use corridors. See the Intersections section of this manual for more information on roundabouts and intersection design.
Dealing with traffic congestion is becoming an inescapable part of daily life in the St. Louis region, especially during the peak hour. Our daily travel patterns are shaped by social and professional structures which create substantial spikes or peaks during the morning and evening rush hour.
Increasing roadway capacity enough to completely eliminate peak period congestion would be unreasonably expensive and have damaging effects on the surrounding residences and businesses. There are, however, measures that can be considered to improve vehicular LOS during peak conditions:
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