In this section, we make conclusions and suggestions about this research. Section 5.1 and 5.2 discuss on conclusions and suggestions, respectively.
5.1 Conclusions
1. Whether in high or low speed period, the errors of travel time estimation and waiting time estimation usually fall in an acceptable range. Therefore, we may say that we have a good estimation result.
2. We may overestimate or underestimate the waiting time of the next intersection, mainly because of the traffic control performed there by the police during peak hours or estimation errors in the present intersection.
In this way, owing to the errors, we may have a bigger error in the following intersections.
3. In some intersections where travel time is shorter, the average absolute error percentage will be higher, but the average error value is still in an acceptable range.
4. Through the analysis method of changing points, we divide the historical average speed database into some different categories by its vehicle speed.
Then we found that it matches the real situations, and can surely improve the model’s domination on them.
5.2 Suggestions
In this section, we make some suggestions for future researches as follows:
1. This study didn’t leave a mark on boarding time, but due to its importance, we suggest that be counted in future researches.
2. Not encountering abnormal situations, so that we didn’t have a chance to test the model in estimateing the travel time in that situation. And we also suggest future researches do some further research on it.
3. Random adjusting of signal timings in intersections makes the errors worse.
Thus, it is recommended to have a further research on it in the future.
4. The transmitting frequency of GPS data effects greatly in estimateing travel time: the errors varies worse as the frequency becomes lower. So, we suggest that future researches think more on it.
Reference
[1] Sen, A., Thakuriah, P.V., Zhu X. Q., and Karr A.. (1997). “Frequency of Probe Reports and Variance of Travel Time Estimates.”, Journal of Transportation Engineering, 123 (4), 290-297.
[2] Jasperse, Diana, van Toorenburg, Jaap, “Real-Time Estimation of Travel- Time and Queue-Lengths – A Practice Study”, Presented at 6th World Congress on Intelligent Transport Systems 1999. Toronto, Canada.
[3] Rosc, Geoff, Paterson, Darryn, “Dynamic Travel Time Estimation on Instrumented Freeways”, Presented at 6th World Congress on Intelligent Transport Systems 1999. Toronto, Canada.
[4] Yamane, Ken’ichiro, Sano, Yutaka, Furuta, Masataka, Fushiki, Takumi,
“Development of Travel Time Estimation System Combining License Plat Recognition AVI and Ultrasonic Vehicle Detectors”, Presented at 6th World Congress on Intelligent Transport Systems 1999. Toronto, Canada.
[5] Bruce R. Hellinga, Liping Fu, “Reducing bias in probe-based arterial link travel time estimates”, Transportation Research-C, No.10, pp 257-273, 2002.
[6] Ashish Sen, Piyushimita (Vonu) Thakuriah, Xia-Quon Zhu, Alan Karr,
“Variances of link travel time estimates: implications for optimal routes”, International Transportations in Operational Research, No.6, pp 75-87,1999.
[7] Ying Lee, “Development of freeway bus travel time forecasting model using artificial neural networks”, master thesis, Department of Transportation and Communication Management Science of National Cheng Kung University, 2001.
[8] Chia-Feng Wu, “The study of Vehicle Travel Time Estimation with GPS
Information provided”, master thesis, Department of Engineering in Traffic and Transportation of National Chiao Tung University, June 2001.
[9] Hui-Wen Chang, “The study of Usung GPS data of Buses to Estimate the Average Speed in a Link”, master thesis, Department of Engineering in Traffic and Transportation of National Chiao Tung University, June 2002.
[10] Sanghoon Bae, “Dynamic Estimation of Travel Time on Arterial Roads Using Automatic Vehicle Location (AVL) Bus as a Vehicle Probe”, Philosophy in Civil Engineering, May 1995.
[11] Chi-Bang Chen, “Dynamic Estimation of Travel Time and Origin-Destination Demand on Freeway Corridor”, master thesis, Department of Transportation Management of Tamkang University, June 2002.
[12] Shih-Chieh Lin, ”The study of freeway bus travel time forecasting model using artificial neural networks”, master thesis, Department of Transportation and
Communication Management Science of National Cheng Kung University, 2001.
[13] Chang Shiou Rong, “The study of freeway bus travel time”, master thesis, Department of Civil Engineering of National Central University, June 2000.
[15] Chung-Tien Kuo, “A Estimateion Model for Bus Arrival Time and Multi-Route”, master thesis, Department of Civil Engineering of National Taiwan University, June 2003.
[16] Matthew P.D’Angelo, Haitham M.Al-Deek , Morgan C.Wang, ”Travel Time Estimateion for Freeway Corridors”, Transportation Research Record 1676, pp 99-1073.
[17] Scot.t Swashburn, Nancy L.Nihan, ”Estimating Link Travel Time with the Mobilizer Video Image Tracking System”, Journal of Transportation Engineering. 1999.Jan.Feb.
[18] Benjamin Coifman, ”Vehicle Re-Identification (VRI) and Travel Time Measurement (TTM) in Real-Time on Freeways Using Existing Loop Detector Infrastructure”, TRR1643, pp.181-191.
[19] Messer C.J. Dudek C.L and Friebele J.D, ”Method For Estimateing Travel Time and other Operational Measures in Real Time During Freeway Incident Conditions ”, HRR461, pp.1-16, 1973.
[20] Carlos. Daganzo, “Properties Of Link Travel Time Functions Under Dynamic Loads ”, Transportation Research-B, Vol. 29 B, No. 2, pp.95-98, 1995.
[21] Benjamin Coifman, Michael Cassidy, “Vehicle reidentification and travel time measurement on congested freeways”, Transportation Research-A, Vol.36 A, No 36, pp
899-917, 2002.
[22] Benjamin Coifman, “Estimating Travel Times and Vehicle Trajectories on Freeways Using Dual Loop Detectors”, Transportation Research-A, Vol.36 A, No 36, pp. 351-364, 2002.
[23] Bruce R. Hellinga, Liping Fu,”Reducing Bias in Probe-Based Arterial Link Travel Time Estimates”, Transportation Research-C, Vol.10 A, No 10, pp. 257-273, 2002.
[24] Karlf. Petty, “Accurate Estimation of Travel Times From Single-Loop Detectors”, Transportation Research-A, Vol.32, No 1, pp. 1-17, 1998.