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Trips Forecasting - Estimation of Trip Generation
Any development will produce additional trips which eventually increase traffic on roads and subsequent congestion or/and reduce safety. The analysis of current situation is important as it may serve as the reference point for determining the impacts of any future development. Analysis should cover issues relating to capacity and the level of service of current transportation infrastructure.
Stages of travel demand model used for trip forecasting
- Trip generation - Trip generation exercise is to estimate the additional trips, produced and attracted by the proposed development. Trip rates or trip regression equations is used. Estimated trips are usually in vehicle trips rather than person trips, and need to be converted to pcu before subsequent analysis. Trips rate is a simple ratio of trips per unit selected variables (eg trips/unit of semi-detached house). Trip regression equation relates generated trips to single or several independent variables such as development size.Trip rates and equations are documented in the Trip Generation Manual, HPU 1997, Malaysia.
- Trip distribution - All generated trips are then distributed to the most likely direction its going to (for trip production) or it is coming from (for trip attraction). It is done by determining the percentage of total trips for different possible directions of origins and destinations
- Trip assignment - Generated trips are then assigned to the road networks adjacent to and around the development. The process must be done before any impact assessment on the surrounding areas can be carried out. The aim of trip assignment is to identify the future volume of traffic on the road network and at junctions, of which subsequent traffic analysis will require.
