Are cooperative and automated vehicles the best course of action?
A statement by Prof. Ing. Ph.D. Ondřej Přibyl, Dean of CTU Faculty of Transportation Sciences, Prague (CZ)
Nowadays, with people moving into cities and increasing vehicle ownership, growing traffic congestion is an issue we face every day. Solutions, such as building new road infrastructure is not always possible, it is costly and clearly not the right way. Already in 1955, Lewis Mumford stated that “Adding car lanes to deal with traffic congestion is like loosening your belt to cure obesity.” This is very true and so the trend is in in the direction of traffic telematics, including also cooperative and automated vehicles (CAVs).
There are many benefits people expect from introducing CAVs, for example improvement in safety, decrease of traffic congestions and travel times, decreased emissions, increased comfort and gained time for relaxation during traveling, decrease in social inequalities and many others. Is this however the case? Can we really expect such improvements?
Just the fact that the vehicle drives by itself does not necessarily have a direct effect on the above-mentioned indicators. Yes, CAVs shall have positive impact on safety as they can eliminate human error, which, according to a Stanford Law School report, causes more than 90 % of all motor vehicle crashes. Similarly, automated vehicles will improve the effectivity of travel, since we will be able to work or relax while on route. It is also a clear fact, that automated vehicles allow new user groups such as elderly, or handicapped to use car as a main travel mode.
But what about traffic congestions? Many studies actually demonstrated that introduction of automated vehicles can lead to an increase in vehicle miles travelled in the network (thanks to trips of empty vehicles or the fact, that new user groups can travel using a car) and even better load balancing can actually induce new traffic by making traveling by car more attractive. Clearly, these factors worsen not only the travel comfort but also lead to an increase in congestions.
Most stakeholders nowadays are looking at improvements in the vehicles, clearly essential in order to have safe automated vehicles – a prerequisite to consider CAVs as an alternative travel mode.
But even when we have the safe automated vehicles, the impact on the traffic flow depends on our integration into the existing traffic management. This was nicely demonstrated for example by a European project MAVEN (Managing Automated Vehicles Enhances Network). In this project partners from several countries examined integration of CAVs into urban traffic management. The use cases tested covered among others Green Light Optimal Speed Advisory (GLOSA), Lane change advisory, Local level routing (LLR), Cooperative sensing, and others. Traffic microscopic simulation was used to demonstrate impact of different penetration rates of automated vehicles, different traffic volumes and different net work configurations on various aspects relate to characteristics of traffic flow, CO2 emissions as well as safety.
The results were in my perception really interesting. On one hand they showed that implementing of some of the use cases really can have an impact, for example on the produced emissions. The effect of load balancing through local level routing reaches up to almost 19 %, signal optimisation reduces CO2 emissions by over 12 % and the speed advisory with novel queue length estimation algorithms over 10%. So even without electrification of or fleet, reduction of the produced emissions can be achieved by better utilisation of CAVs.
There is a long way to get to the full penetration of CAVs on our roads. However, the results show that already in a situation when only 20% of the vehicles are cooperative, the speed advice and green wave implementations lead to decrease of delay by 9 %, decrease of queue length by 6 % or decrease of CO2 by 4 %.
My personal opinion is that CAVs will play an important role in the future (especially its cooperativeness). If we want this role to be positive, we need to adopt the way we manage traffic in cities. Also, we need the vehicles to be not only connected and automated, they should be also electrified and shared. An electric, automated vehicle sitting the whole day in a parking lot in front of my offices, just to drive me in the evening 20 minutes back home, does not change anything. Only if it can pick up other passengers during its idle time, it can really cause less vehicles in the streets or lower the demand for parking spaces.
The needed changes though cannot depend just on our municipalities. I already mentioned that automated vehicles can actually increase the number of vehicle miles travelled. In that case, even more environmentally friendly engines increase the negative impact on the environment. To achieve real improvements, we need to start by ourselves and think about every mile we travel. Is it really necessary? And if so, do we need to take a car (automated or not) or can we use alternative travel mode such a bicycle or public transport?
I hope we, as citizens, as well as the municipality representatives through their policies and urban design, will cooperate on making changes to improve the urban environment and make cities more liveable.
Let us talk about such important topics for example during our next ETC congress organized by CTU and EPTS in May 2023 in Prague.
This article was published in International Transportation | Collection 2022