BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:An investigation of proportionally fair ramp metering - R. J. Gibb
 ens\, Computer Laboratory\, University of Cambridge
DTSTART:20100426T140000Z
DTEND:20100426T150000Z
UID:TALK24582@talks.cam.ac.uk
CONTACT:Neil Walton
DESCRIPTION:This talk concerns ramp metering which is one important approa
 ch to\ndealing with congestion on motorways. Congestion occurs when demand
 \nexceeds available resources and can significantly reduce the capacity\no
 f the motorway network at peak times.  Reduced capacity results in\nadditi
 onal delays\, increased environmental pollution and hinders\npassenger saf
 ety. Congestion is observed to cause low but highly\nvolatile speeds resul
 ting in more uncertain journey times (referred to\nas flow breakdown or st
 op-and-go behaviour).\n\nRamp metering is intended to control the entry of
  new flow in such a\nway as to maintain steady flow on the motorway and to
  avoid the flow\nbreakdown associated with congestion.  The rate of entry 
 of flow is\nset according to the particular ramp metering strategy.  Such\
 nstrategies have been the subject of much attention in the transport\nlite
 rature. One of the key issues is the trade-off between efficiency\nand fai
 r use of resources. This is a trade-off that has been\nconsidered extensiv
 ely in the modelling and control of communication\nnetworks.\n\nThis talk 
 adds to recent work (Kelly & Williams (2010)) on a ramp\nmetering strategy
 \, proportionally fair metering\, inspired by\nrate control mechanisms dev
 eloped for the Internet.  Specifically\, we\nuse simulation results to com
 pare proportionally fair metering with a\ngreedy strategy for a linear net
 work with a series of entry points\nleading towards a single common destin
 ation for all the traffic\, such\nas a radial route towards a city centre.
  Under our modelling\nassumptions\, the greedy strategy is provably optima
 l for exogenously\ndetermined arrival streams of traffic\, but it is unfai
 r\, in a certain\nprecise sense\, between different entry points and may w
 ell have\nperverse and suboptimal consequences if it influences traffic de
 mand.\nWe further consider a network with parallel roads where flows of\nt
 raffic may have route choice according to the levels of queueing at\nthe i
 ndividual entry points.\n\nJOINT WORK WITH F.P. KELLY
LOCATION:Seminar Room 1\, Isaac Newton Institute for Mathematical Sciences
END:VEVENT
END:VCALENDAR