On the use of common random numbers in activity-based travel demand modeling for scenario comparison

ABSTRACT

Activity-based travel demand models provide a high level of detail when modeling complex travel behavior. Since stochastic simulation is used, however, this high level may induce large random fluctuations in the output, necessitating many model reruns to produce reliable output. This may become prohibitive in terms of computation time when comparing travel behavior between multiple scenarios, in which case each scenario requires its own simulation. To alleviate this issue, we study the use of common random numbers, which is a technique that reuses the same random numbers for choices made by travelers between scenarios. This ensures that any observed difference in output across scenarios cannot be attributed to mutual differences in drawn random numbers, eliminating an important source of random fluctuation. We demonstrate by a numerical study that common random numbers can greatly reduce the number of runs needed, and thus also the required computation time, to obtain reliable output.

KEYWORDS:

• Scenario comparison
• common random numbers
• activity-based modeling
• travel demand

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the NWO Gravitation programme NETWORKS [grant number 024.002.003] and TNO, the Netherlands Organisation for Applied Scientific Research (nederlandse organisatie voor wetenschappelijk onderzoek).