What are some of the challenges in evaluating public transport?

The difficulty in the appraisal of public transport projects is well understood.

The main issue relates to accurately identifying and describing the costs and benefits.

Any initiative that improves public transport could be expected to increase public transport use.

Costs are short term (capital infrastructure and vehicles) and long term (operations and maintenance), and low or high cost.

Benefits can be short or longer term, quantifiable in monetary terms or described in qualitative terms and difficult to isolate from a whole range of other factors.

A critical factor in public transport appraisal is forecasting the number of users or patronage.

  • Are the analytical tools used to predict future patronage reliable and robust, and transparent to decision-makers? Have they been subject to peer review?
  • In forecasting future demand, has the transport model been calibrated and validated for public transport? Are mode shifts adequately understood and robustly estimated?
  • Are the assumptions made about future travel behaviour change reasonable, considering emerging technology disruptions?
  • Has optimism bias been adequately considered (under-estimating costs and over-estimating demand and benefits)?

Economic appraisal of public transport projects needs to consider other complementary transport planning and policy considerations that may be occurring, such as parking pricing, or provision of additional road capacity.

Perceived costs of competing modes are an important factor in public transport appraisal. As costs change, the potential for public transport services to retain and attract users will change.

Generally transport users do not consider the ‘real’ costs, rather the ‘perceived’ cost – car users for example tend to ignore sunk costs such as maintenance and depreciation, yet are confronted with the ‘real’ cost of public transport in the form of the fare for each trip. Even though fares are only a small proportion of the real cost.

The level of service provided by the road network, together with the current and future demand on that network, will be reflected in perceived cost of travel for car users.

A useful guide to public transport appraisal is Australian Transport Assessment and Planning guideline M1 – Public Transport (May 2018).

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