*3.5. Travel Time Models*

*H*—the desired headway (sec).

Travel time is one of the major performance indicators, which must be considered in the evaluation of transportation networks. The total vehicle travel time (*TTAIMSUN*, sec) is calculated within AIMSUN based on the network entrance and exit times of all vehicles as follows [35]:

$$TT\_{AIMSIN} = \sum\_{i=1}^{N\_{\rm sys}} (TEX\_i - TEN\_i) \tag{6}$$

where:

*TENi*—the entrance time of vehicle *i* in the network (sec);

*TEXi*—the exit time of vehicle *i* from the network (sec);

*Nsys*—the number of vehicles that cross the system during the considered time period (vehicles).

The total vehicle travel time (*TTSimTra f f ic*, sec) on a given network segment is calculated within SimTraffic based on the total time spent by each vehicle on that segment and the total waiting time by each vehicle to enter that segment as follows [36]:

$$TT\_{SimTraffic} = \sum\_{i=1}^{N\_{sys}} (t\_i + w\_i) \tag{7}$$

where:

*ti*—the time spent by vehicle *i* on a given network segment (sec); *wi*—the waiting time spent by vehicle *i* to enter a given network segment (sec).

#### *3.6. Average Speed Models*

In AIMSUN, the average speed per vehicle (*SAIMSUN*, m/sec) is computed based on the following relationship [35]:

$$S\_{AIMSIN} = \frac{\sum\_{i=1}^{N\_{sys}} S\_i}{N\_{sys}} \tag{8}$$

where:

*Si*—the average speed of vehicle *i* (m/sec).

The average speed of vehicle *i* is estimated as follows [35]:

$$S\_i = \frac{D\_i}{TEX\_i - TEN\_i} \tag{9}$$

where:

*Di*—the total distance traveled by vehicle *i* in the network (m).

In SimTraffic, the average speed per vehicle is computed by dividing the total distance by the total travel time [36]. The average speed is weighted by the vehicle flow and includes the stopped time and denied entry time.
