Papers by Benjamin Heydecker
Elsevier eBooks, 1998
This paper investigates the temporal inflow profile that minimises the total cost of travel for a... more This paper investigates the temporal inflow profile that minimises the total cost of travel for a single route. The problem is formulated to consider the case in which the total demand to be serviced is fixed. The approach used here is a direct calculation of the first order variation of total system cost with respect to variations in the inflow profile. Two traffic models are considered; the bottleneck with deterministic queue and the kinematic wave model. For the bottleneck model a known solution is recovered. The wave model proves more difficult and after eliminating the possibility of a smooth inflow profile the restricted case of constant inflow is solved. As the space of possible profiles is finite dimensional in this case, the standard techniques of calculus apply. We establish a pair of equations that are satisfied simultaneously by the optimal inflow and time of first departure.
Proceedings of the 1995 UTSG Conference, 1995
Keywords: UCL Reference EPFL-CONF-158627 Record created on 2010-11-25, modified on 2016-08-09
Contributors to the project The following people contributed to the present scoping study in thei... more Contributors to the project The following people contributed to the present scoping study in their various ways, as indicated by the grouping. Steering Group Members Suku Phull Department for Transport Suku Phull is currently working as a senior engineer in the Traffic Management division of the Department for Transport. He is responsible for providing the Department's technical and policy lead on all aspects of pedestrian crossing, traffic signal operation and traffic management. He has been responsible for commissioning a number of research and consultancy projects on new and innovative traffic signal control techniques and has been responsible for developing the new Puffin crossing concept. He also played a key role in taking forward some of the actions outlined in the Government's National Motorcycling Strategy, including published guidance on allowing motorcycles access to bus lanes. Ray Yelland London Road Safety Unit Ray Yelland started his career in 1971, and was on the training scheme at the GLC. During this time he moved around different departments, including Highway Design, Traffic Management, and of course Road Safety Engineering. In 1979 he moved to the City of Westminster, as Senior Engineer in the then newly formed Road Safety Section. During the following four years, the team implemented 300 safety schemes which resulted in an overall reduction of 30% in PIA's. In 1984, he moved to the Works and Estimation Section, as Principal Engineer. This role involved the provision of estimated cost of Highway Projects, supervision of contractors and settlement of invoices.
Keywords: UCL Reference EPFL-CONF-158632 Record created on 2010-11-25, modified on 2016-08-09
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Transportation Planning and Technology, Oct 18, 2013
Many analyses of traffic signal queues use Webster and Cobbe's formula, which combines the net ef... more Many analyses of traffic signal queues use Webster and Cobbe's formula, which combines the net effect of the red/green cycle with a term representing stochastic effects, idealised as an M/D/1 queue process having random arrivals and uniform service. Several authors have noted that this component should depend not only on demand intensity but also on throughput capacity in each green period, although an extra empirical term may partially allow for this. Extending the service interval in M/ D/1 (M = Markovian, i.e. random, D = deterministic, i.e. uniform, 1 = one server) enables the effect to be reproduced, but no exact expressions for its moments are found. Approximate formulae for the extended mean exist but are accurate only near saturation. The paper derives novel approximations for the equilibrium mean and also variance and utilisation, using functions linking traffic intensity with green period capacity. With three moments, equilibrium probability distributions can be estimated for which a method based on a doubly nested geometric distribution is described.
Emerald Group Publishing Limited eBooks, Jun 17, 2002
This paper demonstrates how an elastic dynamic equilibrium assignment model can be used in formul... more This paper demonstrates how an elastic dynamic equilibrium assignment model can be used in formulation of equilibrium network design that recognizes the characteristics of network performance under congested conditions. The study identifies first order optimality conditions for the formulation that makes explicit use of derivatives of the equilibrium costs of travel with respect to the amount of travel and the network design parameters. Developed is a novel sensitivity analysis for variations in elements of the design of networks under dynamic equilibrium departure time and route choice, Presented and discussed are the results of a design exercise for a small example network.
Emerald Group Publishing Limited eBooks, Dec 15, 1998
This paper investigates the temporal inflow profile that minimises the total cost of travel for a... more This paper investigates the temporal inflow profile that minimises the total cost of travel for a single route. The problem is formulated to consider the case in which the total demand to be serviced is fixed. The approach used here is a direct calculation of the first order variation of total system cost with respect to variations in the inflow profile. Two traffic models are considered; the bottleneck with deterministic queue and the kinematic wave model. For the bottleneck model a known solution is recovered. The wave model proves more difficult and after eliminating the possibility of a smooth inflow profile the restricted case of constant inflow is solved. As the space of possible profiles is finite dimensional in this case, the standard techniques of calculus apply. We establish a pair of equations that are satisfied simultaneously by the optimal inflow and time of first departure.
Keywords: UCL Reference EPFL-CONF-158634 Record created on 2010-11-25, modified on 2016-08-09
The participants in this workshop included practitioners and researchers from local and national ... more The participants in this workshop included practitioners and researchers from local and national government agencies, consultants, manufacturers and universities in the USA, Canada, West Germany and United Kingdom. Wide ranging discussions on a variety of topics were held. These included the potential offered by new hardware and software technology, and the uses that might be made of this potential; advanced traffic modelling requirements; communication between practitioners and researchers; and research needs. For the covering abstract of the conference see IRRD 832076.
Transportation Planning and Technology, May 13, 2019
Governance theory examines different ways of managing resources and relationships in order to ach... more Governance theory examines different ways of managing resources and relationships in order to achieve a desired outcome. This paper applies governance theory to intermodal terminals and logistics platforms, extending previous work on ownership to include different operational models. An inductive methodology is used to derive a typology of governance relationships from an analysis of the transport and logistics literature. The classification developed in this paper explores different kinds of integration that can help support growth of intermodal transport services. The understanding of transport governance is extended via three key relationships: first, between the logistics platform and the site tenants (therefore, encouraging consolidation and efficiencies that can boost rail services at the site); second, between the terminal operator and rail service provision (which can aid service planning and train loading factors); and third, between the inland site (either terminal, logistics platform or both) and port(s), (thus enabling better planning and efficiency of port rail shuttles).
Transportation research circular, Jun 1, 2011
Keywords: UCL Reference EPFL-CONF-158644 Record created on 2010-11-25, modified on 2016-08-09
Keywords: UCL Reference EPFL-CONF-158649 Record created on 2010-11-25, modified on 2016-08-09
Optimisation of signal timings at a road junction involves the calculation of both continuous and... more Optimisation of signal timings at a road junction involves the calculation of both continuous and discrete variables. The continuous ones correspond to times at which signals change whilst the discrete ones correspond to the order, known as the sequence, in which incompatible streams of traffic receive right of way. The optimisation can thus be formulated as a bi-level programme with discrete variables at the upper level and continuous ones at the lower. The problem which is addressed in this paper is that of identifying a suitable set of values for the discrete variables to be considered for optimisation of the continuous ones. This is achieved by using an exhaustive technique to generate possible sequences and then identifying classes of these that will give rise to identical performance after optimisation of the continuous variables. In practical examples, the equivalence classes are sufficiently large that a considerable saving in computational effort can be achieved by using a single representative from each class. This bi-level formulation has a computational requirement for the optimisation of fixed-time signal-settings which compares favourably with that of mixed-integer ones. A possible extension of this approach to real- time control is noted. (A) For the covering abstract of the conference see IRRD 851540.
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Papers by Benjamin Heydecker