Modelling advanced driver information systems
              in traffic simulation: the PACSIM approach

                      Ph. Dehoux and  Ph.L. Toint

                            February 1991

The   emergence  of  advanced driver   information  systems sets   new
challenges in the area of  traffic modelling and  simulation.  The use
of techniques such as  autonomous   route guidance, advanced  incident
warning or information channels dedicated  to traffic information must
be incorporated in a  new  generation of  traffic models.   This paper
firt discusses  the   impact   of these  new  systems     on modelling
methodology, with an  emphasis on some crucial  issues to make the new
models both realistic  and adaptable to technological and sociological
evolution.

The  main issues  are  the  avoidance  of  the ``steady    state'' and
``perfect  information''   assumptions  commonly    made    in traffic
simulation, the need of an explicit model for traffic information flow
and the modification of  behavioural routing  methods allowing for the
real time  use of  this    information.  These issues   in turn   have
consequences on  more technical  levels, such as network representation
and traffic metaphors.

Some of the choices made in  the context of the  PACSIM model are then
described.   This description focusses  on  the implementation  of the
necessary  dynamic  nature  of the simulation,  on  the definition and
properties of ``packets'' ( considered as a traffic metaphor),  on the
structure  and  operation   of  the  traffic  information network  (as
distinct from  the road network itself) and   finally on  the bi-level
behavioural routing methodology applied in PACSIM.  The  discussion of
these concepts also  requires a  brief introduction to  the notions of
hierarchical  network   abstraction,  perceived networks,  destination
trees and ``rule based'' formalisation of driver behavioural theories.

The last  section of the  paper is finally devoted to  perspectives in
this research, including a discussion of  the necessary integration  of
dynamic demand  models  with the  newly  developed  traffic simulation
tools into global ``integrated dynamic models''.