Doug Weir, Andrew King, Mark Apeldoorn

1. Does road traffic congestion drive PT usage
How should we respond when major projects shift the balance?

2. What we’ll cover….
 Background
 What is road traffic congestion?
 What are its behavioural effects?
 What does this mean for PT?
 How should we respond when
major projects shift the balance?
August 8, 2016

3. The background….
 Examine the relationship between
congestion and PT
 This topic is – surprisingly – not
that well understood
 Tends to be dominated by
partisan arguments
 Scratch the surface and
prompt further work.
August 8, 2016

4. So what is road traffic congestion?
 Delay to vehicles as they impede
each other
 Not a bad thing since it reflects
urban and economic growth
 Recurrent vs non-recurrent
 Becomes problematic as road
system nears capacity and
minor events cause failure.
August 8, 2016

5. What are its behavioural effects?
 Travel time elasticities are quite low:
 -0.2 to -0.3 short run
 -0.3 to -0.45 long run
 Three response strategies:
 Those that maintain the current
travel (including variations to
time, route or mode)
 Those that reduce travel
 Life-style/locational changes
August 8, 2016

6. What are its behavioural effects?
 As individuals respond they
release capacity to others, and
if they switch to another
time/route, reduce capacity
there
 Others respond until capacity
is filled and delays discourage
additional trips
 Rough equilibrium is reached
August 8, 2016

7. What are its behavioural effects?
 Lane km elasticities:
 Range between 0.29 and 1.1
 0.69 average in the long run
 Provide evidence that capacity
is filled by induced demand.
August 8, 2016
Source: Litman (2016)

8. What does this mean for PT?
 Congestion is one of many factors that
influence PT demand
 But not as well understood as
other factors
 Cross-elasticity & diversion
rate indicate sensitivity of PT
demand to car travel time
 Diversion rate of 20%
 Cross elasticity of 0.24
August 8, 2016

9. What does this mean for PT?
 Congestion has different effects
on segregated right of way PT
and on-street PT
 Segregated: congestion makes
PT travel time and reliability
more competitive
 On street: congestion may make
PT travel time and reliability less
competitive (depending on the
degree of priority)
August 8, 2016

10. What does this mean for PT?
 Road projects that reduce car
travel time:
 Can be expected to reduce the
relative attractiveness of
segregated right of way PT
 May improve the relative
attractiveness of on-street PT
 Outcome depends on PT travel
time and reliability
competitiveness under new conditions
August 8, 2016

11. What does this mean for PT?
 Suggested equilibrium
mechanism between car
and PT travel in congested
urban areas
 The equilibrium point may
be at a higher cost point
than previously
August 8, 2016
Source: Mogridge (1997) in Zeibots & Petocz (2005)

12. What does this mean for PT?
 But the evidence is limited:
 Two studies suggest mode shift from train
to road on Sydney road projects
 Some other international
evidence – primarily for train
 Limited bus evidence
 Suggested to account for around
half of induced traffic and an
overall increase in corridor traffic
of up to 2% to 3% (possibly greater).
August 8, 2016

13. How should we respond when major
projects shift the balance?
 Two alternatives:
 Do nothing and expect (and accept)
a fair degree of mode switching
with impacts on the PT
attractiveness and viability
 Invest in equivalent improvements
that improve PT travel times and
reliability and allow PT to remain
a competitive and attractive
alternative to car
August 8, 2016

14. How should we respond when major
projects shift the balance?
 PT improvements could range from
minor enhancements to major
upgrades that match road
improvements (and travel time)
 May be appropriate to reallocate
released road space to PT from
inception before induced travel fills
excess capacity
August 8, 2016

15. How should we respond when major
projects shift the balance?
 But more research is needed
into the relationship between
congestion and PT to enable
better decision making
 The profession must provide
this through better
monitoring and analysis.
August 8, 2016

16. Thank you
August 8, 2016