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 maximum quantity of traffic that could move 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 service, street-running light trail transit 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
There are two major areas of interest related to vehicular LOS:
Planners and designers often refer to the "design year" when considering improvements for a thoroughfare. 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, not a mandate. The nature of the thoroughfares 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 thoroughfare, 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.
Level of Service for Downtown Main Streets:
Characteristics affecting level of service (LOS) for Downtown Main Streets are:
High pedestrian and transit presence in downtown areas requires that we prioritize LOS for those users above LOS for those in cars. Great streets in downtown areas must first and foremost provide safe and efficient use for pedestrians and transit. To do so, planners, designers, and local leaders should focus on the following pedestrian measures:
An important byproduct of thoroughfares designed with high LOS for pedestrians and transit is bicycle accessibility. When automobile travel speeds are slowed, bicycles can usually rely on safe and efficient travel while sharing vehicular travel lanes. Signing and parking design can further improve the environment for bicycles along downtown main streets.
Vehicular LOS must also be considered for downtown areas, as indeed many pedestrians travel to the area by car, making access a priority over mobility through the downtown. The LOS measures of average travel speed and delay can therefore be more flexible since slower speeds are more desirable.
As provisions for safe vehicular operations are considered, it is important to remember that congestion is not necessarily bad and is often unavoidable at peak travel times.
Slower speeds and somewhat longer delays at intersections offer several important benefits to downtown main streets:
Adding vehicular capacity, in an attempt to improve vehicular LOS, through roadway widening makes street crossing for pedestrians more difficult and less safe.
Signal delay will usually increase under such widening due to the increase in walk phase time required for pedestrians to navigate the intersection. Additionally, a higher LOS for transit, pedestrians and bicycles offsets the impacts of lower vehicular LOS by providing many options for travel to and through a downtown area.
Congestion is a reality for most downtown areas, including the downtown areas in the St. Louis region. Social and professional structures contribute to significant spikes in daily travel during the morning and evening rush hour. It is neither feasible nor desirable to design for the elimination of congestion. There are, however, measures that can be considered to improve vehicular LOS during peak conditions:
Current practice at the national level is starting to rely less on LOS as a measure of effectiveness. This is not to say that LOS is not important, but rather that there are other factors that must be considered when evaluating the quality or level of service provided. One such factor is that of "reliability" of the street for travel purposes. Does the thoroughfare operate in a consistent manner from day to day and in the peak conditions? If so, then users of the larger regional network can plan their trips accordingly.
For example, a commuter in the Central West End who needs to travel to Ladue might consider taking Delmar Boulevard through University City.
However, the traveler must consider the typical conditions on Delmar if travel time is important. Knowing that Delmar is usually congested in "The Loop" area, the user will likely choose an alternate route such as Forest Park Parkway to avoid the congestion often present in the Loop. Regular congestion on Delmar through University City actually helps users make better choices about travel patterns. If the congestion was less predictable, the choice would not be as clear and users might be frustrated at the lack of reliability.
PDFs:
Charlotte Urban Street Design Guidelines:
Links:
Other References:
(not currently available in electronic format)