Invited Paper - Simulation and Modeling Methodologies, Technologies and Application - page 10

consumed by a battery electric vehicle for that particular scenario. The units are Watt-
hours unless mentioned otherwise. The original analysis was done with data for a
specific vehicle, but because of the proprietary nature of this data it has been norma-
lized and the results are more qualitative.

3.1 Freeway

Fig. 4 shows the average energy required by 125 battery electric vehicles to travel the
3 mile stretch of freeway at various gradients and traffic flows. The bold lines in Fig.
4 represent the mean energy consumed and the dotted lines represent the 95% confi-
dence interval. It can be seen that gradient has a prominent effect on the energy con-
sumption of a battery electric vehicle. There is a rapid increase in the energy values as
we move from a gradient of -4% to 4%. This is because, the vehicle needs more ener-
gy to climb uphill (positive gradient) and it can gain energy through regenerative
braking while going downhill (negative gradient). Congestion has a much smaller
effect than gradient on energy consumption. There is a slight reduction in energy as
the flow conditions approach a congested scenario. This effect is directly related to
the decrease in the speeds for congested flows.
Table 1 shows the impact of desired speed and the number of lanes on the energy
consumption under different flow regimes. Fig. 5 presents the data in such a way as to
show that vehicle speed is much more significant than the number of lanes. A vehicle
travelling at around 60 mph will consume about 30% more energy than a vehicle
travelling at around 50 mph. Also, the number of lanes on the freeway doesn't seem to
have an effect on the overall energy consumption.

Fig. 4. Energy consumption for vehicle travelling on the freeway at different grades