Does road traffic congestion drive PT usage

How should we respond when major projects shift the balance?

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?

1 May 2023

The background….

Examine the relationship between congestion and PT

This topic is – surprisingly – not that well understood

Tends to be dominated bypartisan arguments

Scratch the surface andprompt further work.

1 May 2023

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 andminor events cause failure.

1 May 2023

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 totime, route or mode)

Those that reduce travel Life-style/locational changes

1 May 2023

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

1 May 2023

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.

1 May 2023

Source: Litman (2016)

What does this mean for PT?

Congestion is one of many factors that influence PT demand

But not as well understood asother factors

Cross-elasticity & diversionrate indicate sensitivity of PTdemand to car travel time Diversion rate of 20% Cross elasticity of 0.24

1 May 2023

What does this mean for PT?

Congestion has different effectson segregated right of way PTand on-street PT Segregated: congestion makes

PT travel time and reliabilitymore competitive

On street: congestion may makePT travel time and reliability lesscompetitive (depending on thedegree of priority)

1 May 2023

What does this mean for PT?

Road projects that reduce cartravel time: Can be expected to reduce the

relative attractiveness ofsegregated right of way PT

May improve the relativeattractiveness of on-street PT

Outcome depends on PT traveltime and reliabilitycompetitiveness under new conditions

1 May 2023

What does this mean for PT?

Suggested equilibriummechanism between carand PT travel in congestedurban areas

The equilibrium point maybe at a higher cost pointthan previously

1 May 2023

Source: Mogridge (1997) in Zeibots & Petocz (2005)

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 anoverall increase in corridor trafficof up to 2% to 3% (possibly greater).

1 May 2023

How should we respond when major projects shift the balance?

Two alternatives: Do nothing and expect (and accept)

a fair degree of mode switchingwith impacts on the PT attractiveness and viability

Invest in equivalent improvements that improve PT travel times and reliability and allow PT to remaina competitive and attractive alternative to car

1 May 2023

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

1 May 2023

How should we respond when major projects shift the balance?

But more research is neededinto the relationship between congestion and PT to enable better decision making

The profession must providethis through bettermonitoring and analysis.

1 May 2023

Thank you

1 May 2023