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Paying for Reliability

Posted 27/02/2020 by Connor Doolittle & Luca Benedini

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Tolling roads has often been predicated on the reduced travel time they offer to users. There is a certain willingness to pay for a shorter journey duration. Cars are nice and comfortable, but we can only bear sitting in them for a limited amount of time.

However, the industry is quickly learning that reduced journey time isn’t the only way to keep road users happy. New research suggests that travellers, shippers, and businesses are equally willing to pay for something else: travel time reliability.

Understanding Travel Time Reliability

Travel time reliability refers to the unexpected delays drivers face on the road. It speaks to the frequency with which such delays occur, and their severity. The United States Federal Highway Administration defines travel time reliability as,

“the consistency or dependability in travel times, as measured form day-to-day, and/or across different times of day.”

In other words, a high variance in the time taken to travel from A to B results in low travel time reliability, which is undesirable to the road user.

An element of fluctuation in road travel times is accepted by most, with drivers allowing extra time to account for delay. This becomes increasingly difficult the lower the travel time reliability. Unsurprisingly, this hits business travellers the hardest – those with meetings, appointments, and shipments to make by a certain time.

The Value of Reliability

Perhaps the most valuable insight into VoR comes from managed lanes, which can be described as a 'freeway-within-a-freeway' where a set of lanes are tolled and separated from the free general-purpose lanes. Manged lanes use different forms of dynamic pricing, based on traffic conditions, to maintain optimal speeds and a steady flow of traffic. The result is high travel time reliability. As such, these lanes are used by those for whom a set journey time has increased value.

Research into tolled roads and managed lanes shows that travel time reliability is something road users are willing to pay for. In order to assess users’ willingness to pay, it has been converted into a monetary unit, called Value of Reliability (VoR). Various studies have attempted to estimate VoR, with most results falling between $5-30 per hour. This figure fluctuates dependent on factors such as trip purpose, monetary advantage, and location.

Such information is crucial when it comes to carrying out traffic forecasts. Value of reliability appears to be just as important a parameter to include as travel time savings.

As such, toll road modelling must go further than before, giving prominence to time saved as well as the consistency with which those time savings are achieved. Our traffic team is experienced in assessing reliability and knowledgeable about its application in traffic forecasting, having both constructed and audited models involving travel time reliability.