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Level of Service

Article

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:

  • For pedestrian LOS, Florida DOT's Pedestrian LOS Model and the City of Charlotte's methodology for pedestrian LOS (TRB's Highway Capacity Manual also has a module for pedestrian LOS)
  • For transit LOS, TRB's Transit Capacity and Quality of Service Manual (TCQSM) (see related documents in thePDFs tab above)
  • For bicycle LOS, the Bicycle LOS Model, the Bicycle Compatibility Index, and the City of Charlotte's methodology for bicycle LOS (see related PDFs) (the Highway Capacity Manual also has a module for bicycle LOS)
  • For vehicular LOS, TRB's Highway Capacity Manual, 2000 edition. TheCity of Charlotte also provides guidance on inclusion of multimodal factorsthat influencevehicular LOS.
Redmond example
Credit: Charlier Associates

Pedestrians

Pedestrian LOS is determined by the following factors:

  • Existence of a sidewalk along the arterial
  • Amount of lateral/horizontal separation betweenpedestrians and motorized traffic
  • Volume of motorized traffic on the arterial
  • Speed of motorized traffic on the arterial

In areas with a significant pedestrian presence, actual pedestrian counts should also be considered.

Transit LOS
Credit: TRB TCQSM

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.

Bicycle LOS
Credit: css.org

Bicycles

Five key variables, listed below in order of importance,are used to determine bicycle LOS:

  • Average effective width of the outside vehicular through-lane of travel (includes striping for bike lanes)
  • Volume of motorized traffic on the arterial
  • Speed of motorized traffic on the arterial
  • Amount of heavy vehicles/trucks on the arterial
  • Condition of pavement over which bicyclists are expected to ride

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:

  • Intersections: Quality and level of service at intersections control the overall quality and level of service for the broader arterial street. The intersections, particularly those signalized, are the points of greatest conflict and greatest safety risk for all modes of travel. Intersection quality and level of service is expressed in the amount of delay experienced at the intersection. It is important to recognize that most traditional evaluation methods are auto-oriented and do not account for the relationship between automobiles and other modes of travel. The City of Charlotte recently developed guidance for measuring signalized intersection level of service in multi-modal settings. The guidance is intended to yield a level of service for vehicular traffic in a way that accounts for pedestrian, bicycle, and transit impacts at the intersection. See the Charlotte Urban Street Design Guide: Vehicular LOS for Multimodal Intersections for more information.
  • Street segments: The street segments are the sections of the arterial street between the intersections. The quality and level of service for street segments is traditionally expressed by the average speed by which vehicles can travel along the particular segment of the arterial street, although as noted above, the efficiency (or lack thereof) of the intersections will control the capacity and LOS of the arterial as a whole. As with intersections, street segment evaluation methods are traditionally focused on vehicular LOS. The City of Charlotte provides good guidance that account for multi-modal needs along the street. See the Charlotte Urban Street Design Guide: Segments for more information.

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 ofhowdevelopment willaffect futuretraffic. 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 Guidesuggests 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 Level of Service for Civic/Educational Corridors:

  • In educational/school areas, the presence of children requires special consideration
  • There is a significant spike in traffic congestion, pedestrian presence, and transit use during morning, lunchtime, and evening rush hours

The rush hour characteristics of these place types present a variety of challenging elements. Employees generally arrive and leave during a concentrated time period in the morning and evening (or at the close of school), with a lesser concentration of travel occurring during the lunch hour as employees/students travel to restaurants or to run errands. In between these three peak periods, travel demand for all modes is usually less. The magnitude of the demand drop off is dependent on the other types of land uses in the area.

The rush hour peaking characteristics described above require planners and designers to have a clear understanding of the travel patternsof all modes during those time periods, bothfor existing conditions and planned future development.

For civic/educational corridorsto become great streets, they must provide safe and efficient transit and pedestrian facilities to accommodate students and employees that commute to work or school via bus or light rail and then walk to their various places of employment/education. To do so, planners, designers, and local leaders should focus on the following pedestrian measures:

  • Provide sidewalks that are continuous and wide enough to provide the desired types of pedestrian services
  • Maximize the amount of lateral/horizontal separation between pedestrians and motorized traffic
  • Keep motorized speeds on the street as low as practicable
  • Provide frequent, reliable, and easily accessibletransit service

Commuting to work or riding to school via bicycle is an increasingly popular mode of transportation. Such travel should be encouraged; it is environmentally responsible, reduces vehicular congestion, and is economically inexpensive for users. As such, attention to quality bicycle LOS is important. The following measures can be taken to enhance bicycle LOS in these civic and educational corridors:

  • Bike lane Credit: css.org Maximize the width of the outside travel lane and provide bike lane striping that is clear and visible, as shown at right. In areas where transit lanes are provided for buses, bike lanes can be well accommodated due to the lower volume experienced in those lanes.
  • Route trucks and heavy vehicles to other truck designated routes tominimize conflicts with bicyclists.
  • Keep motorized speeds on the street as low as practicable.
  • When drainage grates are required, make sure they are visible and "bicycle friendly." Bicycle parking Credit: css.org
  • Provide bicycle racks that are secure and visible to discourage theft, as shown at right.
  • Provide high quality pavement and be vigilant about maintenance and repair; potholes and cracks in the bike lane can have life-threatening consequences for bicyclists.

Transit services are common in these place types. The presence of schools often means a significant presence of school buses. Adequate pick-up and drop-off areas should be provided off of the street so as not to degrade the LOS on the abutting street. Other transit services should consider increased frequency during the peak hours to ensure that services are reliable and that they provide enough capacity for the expected demand.

The desire for good pedestrian, bicycle, and transit LOS must not neglect the provision of quality LOS for vehicular travel. As provisions for safe vehicular operations are considered, it is important to remember that congestion is not necessarily bad. "Gridlock" and complete stoppage of traffic certainly is not good; but slower speeds and somewhat longer delays at intersections offer several important benefits to these place types:

  • Lower speeds create a safer environment for both pedestrians and motorized vehicles. Drivers have more time to perceive conflicts and then react to them.
  • Lower speeds can also allow better progression between signals if the signals are located and timed properly. See the Intersections section of this guide for more detail.
  • Vehicular delay at intersections is in part a result of allowing sufficient time for pedestrians to cross the street. This is a tradeoff worth making in civic/educational corridors.

The presence of educational facilities, especially those serving younger students, requires special attention to pedestrian provision. Pedestrian signal crossing times will likely need to be longer to provide safe crossing for smaller children.

Unfortunately, living with vehicular congestion is becoming an almost inescapable reality in our region. This is especially true in the peak hour. Our culture is predicated on social and professional structures that contribute to significant spikes in daily travel during the morning and evening "rush hour". These spikes in congestion are particularly challenging when they occur in our civic and educational corridors due to the spike in pedestrian travel often occurring at the same time as the spike in vehicular congestion. To eliminate congestion would require unreasonable amounts of money and would have damaging effects on the "places" through which the congested streets run. There are, however, measures that can be considered to improve vehicular LOS during peak conditions:

  • One of the biggest conflicts along arterial street intersections is that of left-turning vehicles (from major on to minor street). During the peak hour or "rush hour" periods, prohibition of left turns that are particularly problematic (can be determined by examination of substantive safety issues) can improve traffic flow and reduce the risk of crashes. If left turn prohibition is not an option, restricting left turns to a "protected only" phase (the phase when opposing traffic is stopped as vehicles are given the green left turn arrow) will eliminate the increased crash risk associated with "permitted" left turns (allowing traffic to turn left when they find what they believe to be an acceptable gap in the opposing traffic stream).
  • During the peak hours, consideration can be given to elimination of the "peak direction" parking lane (if on street parking exists) to add an additional through lane for increased vehicular capacity.Special bus loading zones at school locations may also be considered to replace local parking during peak periods.
  • Encouraging staggered or flexible work hourscan help alleviate some peak hour congestion. Although not all industries are conducive to flexible employee schedules, those that are should consider the benefits of this strategy (and possibly even offer incentives for participation). For schools, it is often unreasonable to stagger the daily schedule too much; however, consideration to such action should be given when examining ways to maximize the safety of students and faculty traveling around the school area on foot during the peak periods.