Travel Time Reliability Benefits on Cost-benefit Analysis – Computation for the Public Transport Lane on the A7 Motorway in Marseille (France)
Damien Grangeon, Cerema Centre-Est, Pierre Nouaille, Cerema Territoires Et Ville
The current French appraisal guidelines propose a methodology to monetize travel time variability gains. The paper proposes to experiment it for public transport passengers with data from the public transport lane on the A7 motorway in Marseille.
Reductions in travel times are generally the main benefits of transport projects in the cost–benefit analysis (CBA). Moreover an increasing range of investments, such as dedicated lanes, are specifically purported to reduce travel time variability. These transport projects aim at reducing the spread of the distribution of travel times but not its expected value, and therefore their benefits fall outside the perimeter of traditional CBA. For example, in France, the current appraisal guidelines allow including the valuation of reliability in CBA, but do not require it (Commissariat général à la stratégie et à la prospective, 2013). Therefore, following their publication in 2014, studies have been started on trying out the recommended methodology to calculate travel time reliability benefits and measuring the effects of its implementation.
The current French appraisal guidelines propose a methodology to monetize travel time variability gains (MEDDE, 2014), distinguishing the computations for car users and for public transport passengers. The approach for public transport users is recommended by the Syndicat des Transports d’Ile-de-France (STIF, 2006). It consists of measuring the number of delays then converting, with the recommended social values, their evolution (in percentage points) into minutes, which are monetized with a value of time. This paper aims to test the method for public transport passengers out on an urban transport project. An ex post analysis is led from the public transport lane on the A7 motorway in Marseille, opened in November 2013.
We proceed in three steps. First, we apply the method to calculate travel time reliability benefits for non-urban bus passengers. Our main source of data is a set of travel time records, collected one month before (September – October 2013) and one year after the opening of the public transport lane (November 2014), for every bus running. Then, we compare our CBA results to a quantitative analysis of the travel times distribution, for every hour of the day (peak, off-peak and evening). These comparisons put on evidence the ability, or disability, of the method to report in the CBA improvements and deteriorations in travel time reliability. Finally, we produce some sensitivity tests in order to highlight the parameters with high stakes for the computation of travel time reliability benefits. The recommended measure for travel time reliability and the social values to convert it into minutes are identified as parameters which have to be tested.
A preview of especially interesting results. We find that 55% of the travel time reliability benefits are explained by the peak hours (7am – 9am and 5pm – 7pm), and 17% by the evening hours (7pm – 12am). Delays longer than 15 minutes are worth over 60% of the travel time reliability benefits, which is oversized with regard to the weight of delays contained between 5 and 15 minutes. The paper also provides some outcomes about the sensitivity of the results to the measure used to quantify travel time variability.
Association for European Transport