Level of Service (Essay Sample)

Level of service (LOS) is an analytical way of measuring the quality of a given intersection, freeway, or road. LOS describes the operating conditions of the facility and depends on a collection of qualitative and quantitative factors. These factors include delay, speed, maneuverability, interruption in traffic, fuel consumption, and more. Intersection LOS depends mainly on the average control delay per vehicle (sec/veh). The LOS of a given intersection can range from level A where delay is minimized (10 or less sec/veh) to level F where delay is very high (more than 80 sec/veh) (Narashima and Mohle, 2001).

Delay is the difference between the actual time of travel and the travel time under ideal conditions. At a signalized intersection, like the subject of this study, the delay measured is only the delay resulting from the phase control, called control delay. This delay includes deceleration, queue move-up time, stop time, and acceleration time. In this study, LOS will be determined by performing turning movement counts (TMC) using a DB-400 board counter manufactured by Jamar, Inc.

1.2 - Background

California State University, Sacramento, wants to investigate the LOS of the intersection at State University Drive South and State University Drive East. This fully actuated signalized intersection is very busy, especially during the peak hours since it services the majority of the schools’ inflow and outflow. The purpose of this study is to estimate the LOS of this intersection and make recommendations to improve the LOS and minimize average control delay. These improvements include changes in intersection geometry, lane groups, and phase configuration and sequencing.

1.3 - Objective

The main objective of this study is to calculate the Peak Hour Volume (V), Peak Hour Factor (PHF), and use Synchro traffic analysis software to determine the LOS for every turn movement at all approaches and the overall LOS of the intersection. The effectiveness of the current geometric and signal configuration of the intersection will be evaluated by analyzing the existing conditions. Based on those results, recommendations will be made in order to achieve a higher LOS.

5.0 Conclusion

The results of this study give an indication of the quality of service of this intersection. The client can use these results as a basis for future improvements to enhance the performance of the intersection minimizing delay and maximizing flow. In addition to increasing the capacity of the intersection by adding new lanes, less expensive improvement can be achieved by adjusting 
geometry and lane groups. A better LOS can also be achieved by optimizing signal phasing and phase durations. V and PHF are key parameters that describe the demand on the intersection and its performance quality at different times in the same day and more importantly at peak hours. It is important to include expected future change in V and PHF when designing an intersection, and provide sufficient amount of lanes for the current traffic demand while allowing future improvement that can be achieved by signal phasing optimization and lane group configuration rather than the addition of lanes that can be difficult because of high cost and right of way (ROW) acquisition.