Level of Service (LOS) E in transportation and traffic engineering is characterized by operating conditions at or near the capacity of the roadway. It represents a threshold where traffic flow becomes unstable and is marked by significant operational issues. Key characteristics of LOS E include:
- Capacity Level Flow: Traffic volumes are at or near the maximum capacity of the road. The flow is unstable, and any minor disruptions can cause significant delays and queues.
- High Density and Slow Speeds: Vehicle density is very high, leading to slow speeds and limited maneuverability. The space between vehicles is minimal, reducing drivers’ comfort and convenience.
- Frequent Stop-and-Go Conditions: Vehicles frequently stop and start, leading to stop-and-go traffic, especially during peak travel times.
- Low Operational Comfort: The driving experience is uncomfortable and stressful due to the high density of vehicles and frequent stopping and starting.
- Long Delays: Delays are long and frequent, with vehicles often waiting for extended periods at intersections or in congested areas. LOS E is generally considered undesirable but may be tolerated during peak hours in urban centers or on heavily congested roadways. At this level, the road is operating at its designed capacity, and any further increase in traffic volume will lead to a breakdown in flow, pushing the conditions towards LOS F. Some agencies accept LOS E on urban roadways at the busiest times, because flow at capacity moves the most vehicles, but most set LOS D as the design target.
LOS in parking design
Parking layouts are not designed to LOS E. The grade appears in parking work when engineers analyze entry and exit lanes, ramps and the intersections next to a garage: at LOS E, peak arrivals or departures are at capacity and any slowdown, such as a slow payment transaction, builds a queue. Designers check that peak operations stay below this point. See PARCS and peak demand.