|Type: Field operational test|
|Countries: Japan||5 test users|
|? partners||? vehicles|
|Active from 2008 to 2010|
|Data catalogue||Tools catalogue|
|Data sets used in this FOT:
||The following tools|
were used in this FOT:
Research project of KEIO University
Details of Field Operational Test
Start date and duration of FOT execution
Japanese Eco-Driving and German Eco-Driving
The performances in terms of fuel consumption reduction and driver behavior are compared between Japanese Eco-Driving and German Eco-Driving using multiple vehicles.
Fuel Consumption Reduction Effect of Eco-Driving
1 Definition of Eco-Driving 1.1 Japanese eco-driving One of the representative eco-driving activities in Japan is “10 tips for fuel-conserving Eco-Driving” promoted by the Eco-Driving Promotion Laison Committee. Japanese eco-driving recommends the drivers to conduct a soft starting with gentle acceleration, called “e-start”, and driving without excessive accelerating and decelerating. This is called Japanese eco-driving.
1.2 German eco-driving German eco-driving recommends the drivers to accelerate quickly to reach the fuel efficient range as fast as possible. Therefore, the biggest difference between Japanese and German eco-driving is how to accelerate when the vehicle starts moving.
2 TS/DS integration for the evaluation of Japanese eco-driving and German eco-driving TS/DS integration is conducted for realizing the driving experiment using DS (Driving Simulator) in which the scenario is generated by TS (Traffic Simulator). The DS used in this study is composed of eight image screens, front, left and right fronts, left and right sides, left and right rear, and backside (Figure 1). A driving image from 10 projectors is projected to these screens. A 360-degree field of view is provided to the driver at the driver seat. The left and right side mirrors and the rearview mirror are the same type as those for actual vehicles, and they capture the image of the reverse screen. Furthermore, swing equipment with six axis is attached to the vehicle body. All the equipment is collectively controlled using the main calculator.
Figure 1. General picture of driving simulator
3 Calculation of fuel consumption The fuel consumption amount is caluculated based on the map shown in Figure 2. This map is included in the vehicle motion simulation software, CarSim. It shows the instantaneous fuel consumption amount (kg/s) for an engine speed and an operation amount on the accelerator of the ordinary motor vehicle with a 2.5-liter gasoline engine. The fuel consumption rate km/l is obtained under the condition that the standard density of gasoline is 0.76 kg/l.
Figure 2. Fuel consumption rate map
4 Overview of the experiments An experimental scenario of a straight open road was developed using TS. The scenario begins with the situation where a vehicle stopping at a traffic light starts moving. It drives straight for 400 m, then must stop at a signalized intersection, and drives straight for 300 m. Each subject got into a DS controlled vehicle which was set that there were vehicles driving in front and at the back. (Figure 3). The preceding and following vehicles run according to the vehicle behavior model programmed in TS, and their speed limit was set at 50 km/h. Figure 4 shows the relationship between velocity and distance as the vehicular swept path of the preceding vehicle. The subjects are five males (age: 22 to 24 years, average age: 22.6 years, standard deviation: 0.8 years). They filled out the questionnaire about their attribution such as age and the experience of eco-driving before the experiment. Table 1 summarizes the attribution of each subject who participated in this experiment.
Figure 3. Illustration of experiment scenario
Figure 4. Relationship between velocity and driving distance of preceding vehicle
Table 1. Subject’s attribution
The subjects drove a total of 15 times, 5 times each with three driving technique, namely, normal driving, Japanese eco-driving, German eco-driving in this order. The reason for this order is because it was considered that Japanese and German eco-driving would affect normal driving if the test with normal driving is carried out after those with Japanese and/or German eco-driving done. The subjects received an instruction on the driving technique and practiced how to drive, before the first test of each driving technique. The instruction is summarized as below.
・Normal driving Drive in the same way as they do in their daily lives.
・Japanese eco-driving 1) Press on the accelerator gently using creep phenomenon to start moving (approximately 20 km/h in 5 seconds) 2) Minimize accelerating and decelerating as much as possible and maintain steady acceleration 3)Release the accelerator early and utilize engine braking actively
・German eco-driving 1)Accelerate as fast as possible (but not too quickly) to reach the fuel efficient velocity range (40 to 80 km/h) 2)Release the accelerator after reaching the fuel efficient velocity range and utilize coasting driving actively
5 Experimental results 5.1 Comparison of travel time in eco-driving The travel time from the starting point to the goal in experimental scenario of Figure 3 was compared between the normal driving, Japanese eco-driving and German eco-driving. The result is shown in Figure 5.
Figure 5. Comparison of travel time (n=25)
Figure 5 shows that the travel time with Japanese eco-driving is longest of all and is longer than that with normal driving by 1.8% (1.4 s), and than that with German eco-driving by 2.1% (1.8 s) (p < 0.1). Why the travel time with Japanese eco-driving is the longest of all is considered to be due to “e-start” which accelerates gently, one of the characteristics of Japanese eco-driving. On the other hand, there is no statistically significant difference in the travel time between German eco-driving which accelerates as fast as possible and normal driving. Based on these findings, the comparisons of German eco-driving and Japanese eco-driving with regard to the way of accelerating reveal that “e-start” used in Japanese eco-driving affects travel time more.
5.2 Comparison of fuel consumption rate in eco-driving
The fuel consumption rates are compared among each of the driving techniques. They are calculated using the fuel consumption rate map, shown in Figure 2, based on the accelerator pedal input and the engine speed obtained from DS. Firstly, the results of the fuel consumption rates with each driving technique are shown in Figure 6.
Figure 6 indicates that the fuel consumption rate with German eco-driving is 4.1% (0.48 km/l) higher than that with normal driving, and also that of Japanese eco-driving is 0.87% (0.1 km/l) lower than that of normal driving. However, no statistically significant differences were observed in these results. It is shown that the fuel consumption rate with German eco-driving is 5.1% (0.56 km/l) higher than that of Japanese eco-driving (p<0.05). In general, it is said that driving with Japanese eco-driving would reduce the fuel consumption rate compared to normal driving. However, the results of this experiment do not indicate that Japanese eco-driving, which minimizes accelerating and decelerating, will reduce the fuel consumption rate when the intervals between intersections are short. Next, we define the state with 1) no accelerator pedal input nor brake pedal input and 2) a negative acceleration as the free wheel state. The ratio of free wheel state, which is the proportion of the driving time in the free wheel state to the total travel time, is calculated. The result is shown in Figure 7. Figure 7 shows that the ratio of free wheel state with German eco-driving is by far the highest, and that with Japanese eco-driving is the lowest (p < 0.01). Additionally, as an example of driving distance and accelerator pedal input in the cases of normal driving, Japanese eco-driving and German eco-driving, the driving data of the third test by Subject A are shown in Figure 8 to 10.
Figure 7. Comparison of ratio of free wheel state with each driving technique (n=25)
Figure 8. Example of accelerator pedal input and driving distance (Normal driving)
Figure 9. Example of accelerator pedal input and driving distance (Japanese eco-driving)
Figure 10. Example of accelerator pedal input and driving distance (German eco-driving)
As shown in Figure 9, with Japanese eco-driving, the duration of the acceleration is long even though the accelerator pedal input is small because Japanese eco-driving utilizes “e-start”, which made its ratio of coasting state small. This can be the reason why the fuel consumption rate with Japanese eco-driving was worse than that with German eco-driving On the other hand, as shown in Figure 10, the fuel consumption rate with German eco-driving is high right after the start because the accelerator pedal input is big at the start. Fuel consumption rate is better than those of the other driving techniques because when it goes into the coasting state, it requires little fuel consumption after that. Thus, this study suggested that Japanese eco-driving would not always have an effect to reduce the fuel consumption rate compared to normal driving if a vehicle starts moving and stops within a short distance.
5.3 Comparison of driving behavior in eco-driving Figure 11 shows inter-vehicular distance with the preceding vehicle for each driving technique. Comparison of each driving techniques based on this Figure shows the trend that Japanese eco-driving created longer inter-vehicular distance than normal driving and German eco-driving.
Figure 11. Relationship between velocity and inter-vehicle distance
As shown in Figure 11, comparison of each driving technique with regard to the inter-vehicle distance indicates that the distance with Japanese eco-driving is twice as long as those of normal driving and German eco-driving. In addition, a comparison of each driving techniques shows that the inter-vehicle distance with Japanese eco-driving varies far more widely than those with the others. 6 Conclusion The result indicated that German eco-driving reduced the fuel consumption rate by approximately 4% compared to Japanese eco-driving. In addition, there were no statistically significant differences between normal driving and Japanese eco-driving or German eco-driving. This result suggests that Japanese eco-driving would not be always helpful to reduce the fuel consumption rate if the distance from the start to stopping is shortened due to a traffic signal, or other reasons
The performances of Eco-Driving are tested under the condition that the foregoing and following vehicles exist. Under such practical conditions, the fuel consumption reduction rates of Eco-Driving are not significantly large as usually expected.
Summary, type of funding and budget
Cooperation partners and contact persons
Shuichi MATSUMOTO. Ph.D. Senior Assistant Professor Faculty of Science and Technology Keio University mail: email@example.com
Main Contact person
Applications and equipment
Eco-driving (Japanese Style Eco-Driving and German Style Eco-Driving) performances.
The DS (Driving Simulator) controlled vehicle plus the following and the foregoing vehicles controlled by the TS (Traffic Simulator)
Equipment carried by test users
Traffic Simulator and Driving Simulator Integration. Driving Simulator generates the scene according to the scnario of Traffic Simulator and also the reaction of driver will be the input to the Traffic Simulator to generate the next synchronized scenatio.
Pre-simulation / Piloting of the FOT
Method for the baseline
Techniques for measurement and data collection
The data of travel time, delayed time, stopping time and overage velocity are obtained from TS. The data of acceleration, velocity, engine r.p.m., accelerator pedal input, brake pedal input and the position of the vehicle of the DS are obtained from DS controller.
Recruitment goals and methods
Methods for the liaison with the drivers during the FOT execution
Methods for data analysis, evaluation, synthesis and conclusions
Statistical Analysis, Experimental Designs.