Uncertainty Ahead

The next few years are likely to see major changes in the types of vehicles on our roads. How will this affect transport modelling and air quality assessments? Can we predict what is round the next corner? Our highways & transport associate Neal Murphy explores the future of vehicles and reducing emissions.

The government is proposing an end to sales of new petrol and diesel vehicles in 2040. Some organisations are calling for this to be brought forward to 2030. Personally, I think change will happen much quicker than many people anticipate, and that by the mid 2020’s a high proportion of vehicles on our roads will be capable of zero emissions.


Data collated by ‘Next Green Car’ using figures published each month by the Society of Motor Manufacturers and Traders (SMMT) show that electric car sales in the UK have risen dramatically over the past few years. By the end of 2017, more than 47,000 plug-in cars had been registered over the course of the year, representing 1.9% of the total new car market in the UK.


I have been driving electric cars for three years and at the start it was rare to see another electric vehicle on my daily journeys. Now it is common to see a range of electric cars and a wide variety of makes and models. The rate of change in the type of vehicles on our roads should not be underestimated.


The potential for an earlier, swifter update of zero-emission vehicles is suggested by Chargemaster; a UK market leader in electric car charging. It predicts that there will be one million electric cars in the UK by the end of 2022, accounting for around 10% of all new registrations. Its forecasts also suggest that nearly one in four new cars will be electric by 2025, with plug-in cars making up around 50% of new registrations by 2027 and 60% by 2030.


A key input assumption when considering the environmental impact of road transport is the petrol/diesel sales mix and uptake rates of hybrid and electric cars. The WebTAG Databook provides UK transport modelling values and information including projections on how the UK’s modal mix is expected to change over time. The 2016 dataset predicted around 5% of vehicle kilometres would be powered by electricity in 2035. The 2017 dataset increased this prediction to over 13%.


One thing that strikes me about the data is the potential level of uncertainty in these forecasts that could significantly underestimate the popularity of electric vehicles in the coming years. The projections are also presented to two decimal places. But is appearing to be precise concealing the uncertainty and perhaps over-reaching in terms of accuracy?


Advances in technology is driving changes in the form of vehicle automation and artificial intelligence. How will autonomous vehicle technology affect the demand for vehicles and the demand for trips? Will this technology increase the congestion on our roads due to its popularity or will it help to ease traffic flow through intelligent management of the available road space? Will there be a need or desire to travel more or less in the future? Will changes in the future cost or ease of travel mean there are more or fewer trips? Will future communities be localised and rely on walking and cycling or will long-distance trips become more popular due to the comfort and ease that autonomous vehicles could bring?


These advances in technology could, and almost certainly will, disrupt transport in the future. There is great uncertainty as to the type and volume of vehicles that will be on the road network in the future. So, can you really predict traffic forecasts to fractions of a percentage point? Transport planners and traffic modellers should note the uncertainty in the data sources and take account of this when attempting to predict the future.


The only thing which is certain is that the future is uncertain.