## 4 Evaluation
### Results  
Finally, the effectiveness of the IDHIL simulator is demonstrated by comparing the evaluated results for two cases: (1) normal HEV, and (2) CHEV. Commonly, most of the fuel consumption of the vehicle occurs when the engine is running due to acceleration. To compare the fuel consumption according to frequency and extent of acceleration and deceleration of a vehicle between the two cases, we set up a scenario to have several conditions. (1) There was one vehicle, i.e., the HV, and five traffic lights. (2) To highlight the effect of V2I communication on the fuel consumption, there should be an obvious difference in the extent of acceleration and deceleration of a vehicle between the two cases. Therefore, the signal timings of the each traffic light were set to prevent the CHEV from stopping at the traffic lights and to let the normal HEV stopping at the traffic lights, and thus the driver always perceived the red signal phase, which was going to turn green signal phase soon, when entering each intersection. (3) The driver tried to drive at the speed limit or eco-speed. (4) In general, an eco-driving system is evaluated by considering the combination of travel time, travel distance, and fuel consumption. In this experiment, to evaluate the proposed cooperative eco-driving system by comparing only the fuel consumption, the travel time and distance in both cases were same, respectively. Figure 8 shows the driving speed of the normal HEV during simulation. The signal phase and timing information of each traffic light at the time of approaching the traffic light is also shown at the top of the graph. The time when the signal phase of the traffic light changes to green is 60 s, 130 s, 220 s, 305 s, 370 s, from the first to the fifth traffic light, respectively. The normal HEV was not provided with the eco-speed, so the driver drove at the speed limit until perceiving the traffic light. Since it was a manual driving, the acceleration and deceleration occurred frequently for maintaining the speed limit. The normal HEV perceived a red signal phase 50 m ahead of the traffic light, and then decelerated to stop at the stop line. It waits an average of 20 s at the stop line until the red signal phase changes to the green signal phase, and then accelerated rapidly to speed limit. Figure 9 shows the driving speed of the CHEV at the eco-speed. In the case of CHEV, the driver was provided with the eco-speed, which is the result of the operation of the cooperative eco-driving speed guidance application, so the driver drove at the eco-speed. Whenever the CHEV entered the communication range of the traffic light, the application noticed that the signal phase was going to turn green signal phase soon after the red signal phase by using the received SPaT message, and the application provided the calculated eco-speed to the driver. When the CHEV received the SPaT message of the first traffic light, the remaining time of the red signal phase was 30 s and the distance \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Total distance & 4.7 km \\ Speed limit of road & 60 km/h \\ Number of traffic light & 5 \\ Data rate of DUT & 6 Mbps \\ Transmission power of DUT & 26 dBm \\ Communication range & 300 m \\ Vehicle type & TMED-type HEV \\ Vehicle weight & 1880 kg \\ \hline Engine & Displacement & 2900 cc \\ Maximum power & 185 kW \\ \hline Motor & Maximum power & 38 kW \\ Maximum torque & 205 Nm \\ Maximum rpm & 6000 \\ \hline Battery & Rated voltage & 270 V \\ Rated capacity & 5.5 Ah \\ Maximum power & 56 kW \\ \hline \end{tabular}
\end{table} 
Table 1: Parameters in cooperative eco-driving speed guidance application simulation. was 300 m, so the application provided 36 km/h as the eco-speed that enabled the CHEV to pass through the intersection without stopping. The eco-speed was modified in real-time considering the current vehicle speed because the manual driving made it difficult to maintain the guided eco-speed accurately.