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SUMMARY:Do New Roads Generate Traffic? - Charlene Rohr\, RAND Europe
DTSTART:20090305T160000Z
DTEND:20090305T170000Z
UID:TALK16639@talks.cam.ac.uk
CONTACT:8419
DESCRIPTION:Until relatively recent years the traffic and economic apprais
 al\nmethods used for trunk road schemes have assumed that reassignment\n(i
 .e. making the same journey by a different route) was the only\nsignifican
 t impact on trip making behaviour resulting from trunk road\ninvestment.  
 This assumption is no longer generally accepted\, as\nempirical and theore
 tical research suggests that\, both in the short\nand longer term\, a wide
 r range of responses takes place in addition to\nreassignment.  While the 
 extent of these responses has been unclear\,\ntheory suggests that in some
  circumstances they could have a\nsignificant impact on the economic benef
 its of schemes. These\nresponses (collectively referred to as induced traf
 fic effects)\ninclude: rescheduling of trips to take advantage of improved
 \nconditions at peak periods\; increasing frequency of trips\; decreasing\
 nvehicle occupancy\; switching between public transport and private\nvehic
 les (mode shift)\; travelling to new destinations\; making entirely\nnew v
 ehicle trips and changes in the patterns of land use or car\nownership.\nT
 he opening of the M60 Manchester Motorway Box (MMB) completed one of\nthe 
 last major links in the UK motorway network and the scale of the\nnew road
  scheme meant that its completion in October 2000 gave an\nopportunity to 
 collect data concerning the extent of induced traffic.\nPreliminary studie
 s undertaken in 1996 recommended and designed a\nprogramme of Before (1999
 ) and After (2003) surveys comprising\nlarge-scale Roadside Interviews and
  public transport surveys.\nAdditionally\, a large-scale home interview su
 rvey was conducted in\n2002.  Together\, these surveys provide a large and
  comprehensive data\nbase for analysis and modelling.\n\nIn 2005\, RAND Eu
 rope was commissioned to develop models to quantify\nthe magnitudes of the
  different induced traffic effects.  Because the\nsize of some of these in
 duced effects was not known beforehand\, we\nadopted an approach which mad
 e use of the full variance present in the\ndata by preserving the individu
 al observations from the intercept\nsurveys and home interviews.  The pool
 ing of these two very different\ntypes of data added to the complexity of 
 the modelling\, and complex\nweighting procedures were required to take in
 to account that the\nintercept surveys are biased towards long trips.  The
  final models\nwere of high quality\, in terms of the statistical reliabil
 ity of the\nparameters\, the expectation regarding the relative sizes of\n
 parameters\, the ability of the model to predict observed trip lengths\nan
 d the resulting model elasticities.\n\nModel runs were undertaken for two 
 travel purposes: commuting and\nother travel\, using the travel time chang
 es observed from the\nManchester Motorway Box to examine the size of the i
 nduced traffic\,\nand the relative impacts of different behavioural respon
 ses.\n\nThis presentation describes the study background\, the available d
 ata\,\nand\, briefly\, the modelling estimation framework\, before going o
 n to\npresent the results from applying the model to give an indication of
 \nthe relative size of the induced traffic effects as a result of the\ncom
 pletion of the Manchester Motorway Box. The results show a\nsignificant in
 crease in traffic between areas served by the new road\nand reinforce the 
 need for transport planners to take account of\ninduced traffic effects wh
 en considering the benefits of new transport\ninfrastructure.\n\n\n\n
LOCATION:MR13\, CMS\, Wilberforce Road\, Cambridge\, CB3 0WB
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