This post was the fourth in a weekly series of five “what-if?” suggestions proposed in parallel over the festive season 2015-16, that seek to provoke your thoughts about solutions to the traffic impacts of the development on Westgate, but which may also never see the day.

[Apologies if the following analysis is rather hard to grasp. Traffic congestion is a very difficult subject to understand and explain and even the so-called experts will come up with different views to explain this subject.]

There are two issues to address in answering this question:

  • Why has there been little increase of traffic in Westgate in recent years?
  • Will peak spreading occur in future?

Why has there been little increase of traffic in Westgate in recent years?

  • The majority of traffic at present generated on to Chichester roads is during the current AM and PM peak periods (not necessarily an hour).
  • In the past these periods have become longer.
  • In the case of many local roads such as Westgate there is a limit as to how much traffic they can carry.
  • This is governed by the many factors I have previously listed such as junction capacity, effective carriageway width and traffic calming.
  • Many roads are already running at their operational capacity during peak periods and can take no more traffic during these periods.
  • Others are not and may remain attractive for some drivers resulting in rat-running or other journey changes.

However it is important to look at the types and timing of vehicular trips that are undertaken, as follows:

  • Recreational and shopping trips mostly occur outside of peak periods (off-peak trips) so generally do not contribute to peak period congestion.
  • Most recreational and shopping trips are undertaken on roads that are far less congested at the time of travel (i.e. the roads have reserve capacity in off-peak periods).
  • The majority of trips that do occur and contribute to peak hour congestion are journeys to work and to school.
  • These are relatively inflexible and generally have to be completed by a specific time in the current peak period.

But, car ownership has increased in recent years and journeys to work and to school have also increased.

So, why has the traffic in Westgate not increased?

  • It is suggested that it has increased in past years when there was some reserve capacity in Westgate but not in recent years.
  • There came a point when this increasing traffic resulted in some unacceptable congestion at critical points, such as the junctions at each end of Westgate.
  • In turn this resulted in some drivers being more flexible in their journey times; allowing more time for travel or starting earlier or later.
  • This will have extended the length of the peak period at that time.
  • However, a point was also reached prior to 2010 where (work and school trip) drivers were no longer willing or able to drive outside of this extended peak period and it became a relatively fixed duration.
  • As a result many of these drivers decided to use other perceivably more attractive routes or change their mode of transport.
  • So, from this point until now Westgate has been running to its full potential in terms of managing the peak period traffic demand and there is little increase in traffic being recorded.

N.B. Should the capacity of the Sherborne Road/Westgate junction be improved and that of the Westgate/A286 junction then this will encourage some drivers to return back to using Westgate, thereby once more resulting in further increases in traffic flow.

Will peak spreading occur in future and will traffic flows increase in Westgate?

  • Inevitably there will be more demand for vehicular travel especially with the traffic generated from WHF and other major developments approved in the local plan.
  • How this will effect Westgate and other local roads very much depends on how more or less attractive they become as a result of improved capacity of local road junctions or increased restraint such as truly effective traffic calming.
  • For the limited peak period reasons explained above I doubt if there will be an extended peak hour spreading in future on Westgate.
  • But, there may well be an increase in traffic during off-peak periods since Westgate will continue to have reserve capacity to accommodate future increasing traffic demand.

Next traffic post

Colin Hicks

Site Admin - Westgate Residents' Association Chichester

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