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How much is too much for tolled road users:

Updated: Nov 20, 2018

toll saturation and the implications for car commuting value of travel time savings

15 JAN 2016 (FRI) | 18:30-19:30

Room 2.58, Central Podium Level, Centennial Campus, The University of Hong Kong.



Professor David A. Hensher

Institute of Transport and Logistics Studies, The University of Sydney Business School, The University of Sydney NSW Australia (

David Hensher is Professor of Management, and Founding Director of the Institute of Transport and Logistics Studies (ITLS): The Australian Key Centre of Teaching and Research in Transport Management at The University of Sydney. David is a Fellow of the Academy of Social Sciences in Australia (FASSA), Recipient of the 2009 IATBR (International Association of Travel Behaviour Research) Lifetime Achievement Award in recognition for his long-standing and exceptional contribution to IATBR as well as to the wider travel behaviour community. Recipient of the 2006 Engineers Australia Transport Medal for lifelong contribution to transportation, recipient of the 2009 Bus NSW (Bus and Coach Association) Outstanding Contribution to Industry Award, and Recipient of the 2012 best paper released by the International Association of Maritime Economists (IAME). David is also the recipient of the Smart 2013 Premier Award for Excellence in Supply Chain Management, and recipient of the 2014 Institute of Transportation Engineers (Australia and New Zealand) Transport Profession Award. Member of Singapore Land Transport Authority International Advisory Panel (Chaired by Minister of Transport), and Past President of the International Association of Travel Behaviour Research. David is the Co-Founder of The International Conference in Competition and Ownership of Land Passenger Transport (the Thredbo Series), now in its 23rd year. David is on the editorial boards of 10 of the leading transport journals and Area Editor of Transport Reviews. He is also series and volume editor of a handbook series "Handbooks in Transport”. He has published extensively (over 570 papers) in the leading international transport journals and key journals in economics as well as 12 books. He has over 28,800 citations of his contributions in Google scholar. David has advised numerous government industry agencies, with a recent appointment to Infrastructure Australia’s reference panel on public transport, and is called upon regularly by the media for commentary. Most recent roles include expert adviser to WestConnex (a 33 km toll road in planning in Sydney), the expert adviser to the Singapore update of economic parameters (with Aecom), and adviser to Deloittes on congestion intervention strategies (for AustRoads). More information is available at



The current practice of forecasting the demand for new tolled roads typically assumes that car users are prepared to pay a higher toll for a shorter journey, and they will keep doing so as long as the toll cost is not higher than their current value of travel time savings. Practice ignores the possibility that there could be a point when motorists stop driving on toll roads due to a toll budget constraint. The unconstrained toll budget assumption may be valid in networks where the addition of a new toll road does not result in a binding budget constraint that car users may have for using toll roads (although it could also be invoked for existing tolled routes through a reduction in use of a tolled route). In a road network like Sydney which offers a growing number of (linked) tolled roads, the binding budget constraint may be invoked, and hence including additional toll links might in turn reduce the car users’ willingness to pay for toll roads to save the same amount of travel time. When this occurs, car users are said to reach a toll saturation point (or threshold) and begin to consider avoiding one or more toll roads. Whilst toll saturation has important implications for demand forecasting and planning of toll roads, this type of behaviour has not been explored in the literature. We investigate the influence that increasing toll outlays has on preferences of car commuters to use one or more tolled roads as the number of tolled roads increases. The Sydney metropolitan area offers a unique laboratory to test this phenomenon, with nine tolled roads currently in place and another five in planning. The evidence supports the hypothesis that the value of travel time savings decreases as a consequence of toll saturation.



Becky P.Y. Loo

Director, Institute of Transport Studies, The University of Hong Kong

Organizers:The Institute of Transport Studies (HKU)

Department of Geography (HKU)

Hong Kong Society for Transportation Studies


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