Trip Distribution Gravity Model of Al-Diwaniyah City: A Case Study
The main objective of this study is the construction of trip distribution models for allotting trips from each traffic analysis zone to each other in the study area. For this purpose, the city of Al-Diwaniyah in Iraq has been separated into five subdivisions with 70 traffic analysis zones covering a total area of 52 km2. Surveys were conducted throughout prearrangements with high schools, administrations, and some colleges. Five hundred questionnaires were distributed in the city with a response rate of 78.4%. Standard TransCAD Gravity Model software version 4.5 was used in the trip distribution modeling process. The gamma function was adopted for developing the friction factors for Al-Diwaniyah. The gamma coefficients were obtained for five trips purposes in Al-Diwaniyah. The friction factors were determined for up to 60 min using one-minute intervals. With increased travel time, friction factors decrease when the gamma coefficients (b and c) have negative values. The average trip length for the gravity model is range between 12.5 and 18.5 min for the five trip’s purpose that was considered in the study. The trip Length frequency distribution (TLFD) of a home base work trip is 20–25 min. Home base educational trips have two ranges: 11–15 min for short trips (schools within the same zone) and 16–20 min for long trips. The home base shopping trips have an average TLFD of 6–10 min because the shopping destinations are within the TAZs.
KeywordsTravel time Trip distribution TransCAD Traffic analysis zone (TAZ) Friction factor Gravity model
The authors would like to acknowledge the partial support provided by Mustansiriyah University through Highway and Transportation Engineering Department.
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