Analyzing Travel Time Reliability: Data and Analysis Methods

Figure 1. Long Description

This figure shows how the seven sources of congestion interact with each other to yield total congestion and travel time reliability. The seven sources are: (1) physical capacity, (2) fluctuations in demand, (3) traffic control devices, (4) special events, (5) weather, (6) incidents, and (7) work zones. The starting point is the interaction of physical capacity and demand to produce base delay. The other congestion sources, which are highly variable from day-to-day, are layered on top this based delay and this causes variation in total congestion from day-to-day. This variation in congestion is defines travel time reliability.