Automotive

The pros and cons of a driverless future

Despite obvious advantages, the era of autonomous vehicles may not be all plain sailing (Photo: Shutterstock)
Despite obvious advantages, the era of autonomous vehicles may not be all plain sailing (Photo: Shutterstock)
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Despite obvious advantages, the era of autonomous vehicles may not be all plain sailing (Photo: Shutterstock)
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Despite obvious advantages, the era of autonomous vehicles may not be all plain sailing (Photo: Shutterstock)

It may seem as if the only arguments against self-driving cars come from two kinds of people – those fearful of any scenario where they might have to forgo control behind the wheel and those who distrust all technology out of hand. Lolling about while a computer gets you through traffic has its attractions for many of us and there has been little discussion about the potential downsides of a driverless future, but a new study has pointed out some potential flaws in this looming auto utopia.

The upsides seem pretty self-evident. The first advantage of driverless cars is one of multitasking. While being taken from here to there in a driverless car, you can do anything you want. Eat, sleep, work, chat with relatives – commute time is no longer down time.

Then there's safety. Although this has yet to be born out, the theory goes that people, on the whole, are not the best drivers out there. We might all think we're Mario Andretti behind the wheel, but sadly and all too obviously, we are not. By leaving the driving to a whole slew of computers, sensors, servos and software, getting from home to office should be rendered accident free.

The other potential plus is efficiently. While a driverless car is using its digital prowess to whisk you to the store, it can, and will, be talking to all the other driverless cars out there. And not only chatting with them, but talking back and forth with smart roadways. This will allow all sorts of efficiencies to be realized. One driverless car will know that the other driverless cars in front of them will not suddenly slow down, so the gaps between can be shortened. And the first driverless car in this line, when it realizes that it will have to slow down, or stop, will relay this information to all the other driverless cars in the line, and they can react as a unit. Intelligent roadways will allow the timing of traffic lights to be optimized to the known level of traffic density and speed.

Swoosh, off you go! From home to office to store and back home again with nary a red light to be seen along the way!

Scott Le Vine, Alireza Zolfagharib, and John Polak have a different take. The researchers from the Department of Geography at SUNY in New Paltz, New York and at the Centre for Transport Studies, Department of Civil and Environmental Engineering, Imperial College London, have recently published a study that, while not slamming on the brakes for self-driving cars, does point out that it might not all be a smooth road ahead.

"Autonomous cars are expected to increase road network capacity and reduce the disutility of travel time," but " ... under certain circumstances these benefits may be in conflict."

The study examined how two of the three stated benefits – more comfort and less traffic – can live together by running a computer simulation of how driverless cars would work in practice, and comparing that to trains.

Commuter trains are used in many the same ways as driverless cars; you get in, sit down, and read a book or do some work on your commute. Trains work very well for this because trains are smooth. Once they are up and running, they are relatively much more comfortable environment over the stretch of a commute than cars, even driverless ones, could potentially be.

It is that potential problem that the study points to. If driverless cars do a lot of stop/start work like normal cars, even at a reduced velocity, they will become a less workable environment. But, if they speed up and slow down more smoothly for the passenger's sake, essentially mimicking the acceleration and deceleration of trains, then self driving cars would forfeit much of their capacity to alleviate congestion in the process.

"Acceleration has big impacts on congestion at intersections because it describes how quickly a vehicle begins to move," says lead researcher Scott Le Vine. "Think about being stuck behind an 18-wheeler when the light turns green. It accelerates very slowly, which means that you're delayed much more than if you were behind a car that accelerated quickly."

The team replicated traffic at a run of the mill four-way urban intersection where 25 percent of the vehicles were driverless. In some simulations, the driverless cars traveled the way that light rail trains do, gently on the gas then gently on the brakes. In other words more comfortable than a normal car, but still herky-jerky at times. In other scenarios, the driverless rides started and stopped like a high-speed rail train: smoothness in all things.

Le Vine and colleagues tinkered with a number of parameters such as longer yellow lights or following distances. They modeled 16 scenarios against a control group with all human-driven cars, running each simulation for an hour and repeating it 100 times. They considered the normal influence each situation had on traffic with regards to delays and road capacity.

The bottom line was this: In every single test, self driving cars where calculated to create a comfortable, rail-like ride made congestion worse than it would have been in a baseline scenario with people behind every wheel.

When driverless cars accelerated and decelerated in the style of light rail, the congestion deteriorated from 4 percent to 50 percent and the number of cars traveling through the intersection also fell between 4 percent and 21 percent. Going for high speed rail style of smoothness, those numbers got even worse: Delays increased from 36 percent to nearly 2,000 percent and intersection capacity fell between 18 percent and 53 percent.

"Our findings suggest a tension in the short run between these two anticipated benefits (more productive use of travel time and increased network capacity), at least in certain circumstances," say the researchers. "It was found that the trade-off between capacity and passenger-comfort is greater if autonomous car occupants program their vehicles to keep within the constraints of HSR (in comparison to LRT)."

It is also worth pointing out that these simulations just involved normal cars and driverless cars. There were no trucks, buses or, that even more chaotic element, pedestrians.

As a single simulation-based study, the research may not add up to a crippling blow for driverless car advocates, but it shows that there's work to be done in order find a liveable recipe for the coming mix of autonomous and conventional vehicles on our roads.

Source: Autonomous cars: The tension between occupant experience and intersection capacity (Science Direct) via The Atlantic.

27 comments
Deres
Another point not taken into account when comparing manual and automated driving is the way safety is implemented. in current public transport, safety use an absolute vision of safety while in driven cars, it is highly probabilistic. The main example, but it is not the only one is the criteria for the distance between cars. Trains respect the "brick wall" criteria. This means they admit that the preceding train can stop immediatly, as if i has zero speed. This failure scenario has been verified before in many accident. On the contrary, when we drive, we make the assumptions that the preceding car will brake as our car, so only the reaction time is taken into account. Moreover, an automatic system will have to take into account many degraded parameters that it does not know. The state of its brake, the adherence level, the quality of brakes of the preceding car, accident, brutal failures, ... We currently does not really take those into account. Thus, the increased safety of automated could come with a sharp decrease in efficiency. A trade-off will have to be found. And the safety may not increase a lot in this case.
KenCrawford
The study cited is not meaningful in any practical way for two reasons: One, it assumes "autonomously-operating (without vehicle-to-X communication)" vehicles, which I don't think anyone is contemplating, in the medium to long term, i.e. when autonomous vehicles become common. Second, it is rather absurd to compare acceleration speeds of private vehicles in traffic to those of public transportation systems with almost full freedom in this parameter, and the inescapability of very gradual acceleration due to their weight. Cars on congested city thoroughfares will simply not match those acceleration rates, period, and nobody will expect them to. It is also a cheat to eliminate heavy road vehicles from the simulations, since last I noted, they exist. If the point was to prove that trains are more comfortable to work in than cars, I think we knew that.
mikbert
I suspect that some of the groups responsible for publishing the study likely have biases against self-driving cars or, gasp, financial motivation for for showing reasons for not adopting them. A great deal of public money goes into planning for trains and buses. These people have spent their entire professional careers training and planning the use of conventional public transit options. Then this disruptive technology comes along and turns everything upside down. If fewer people need to rely on trains and buses, their roles as public planners are diminished, thus, less money goes to their departments, job cuts, etc. The simplistic model does not account for highway use or that one stupid driver whom decides to turn left on a one or two lane road, blocking all traffic instead of driving one block further to get the dedicated turn lane. It does not account for the autonomous car's ability to redirect traffic well before reaching the intersection when said intersection becomes saturated.
Rehab
The only reason for driverless cars in the city is to allow people to use their smart phones. Great idea for highway driving, as one could arrive rested or let auto handle the chores through the night. Could see long haul trucks pulling up to 10 trailers all linked together with electric power units added in as needed. Would make highways safer and bring down shipping costs.
phissith
Human can't help to fiddle with technology and progress. Yes even atomic bombs. Technology is here to stay and will get better over time. Having fear is healthy and good when put in its prospective but those who don't give credit when its due is just ignorance. Traffic lights are a great a example,totally automated.
YukonJack
This report is obviously only half done as it hasn't shown any real life studies. We all know about drawing boards in offices with no windows to reality.
zevulon
studies like this are good reason to be very skeptical of academic studies, and of where your tax dollars go in supporting think tanks, and of the 501c3 structure generally. there are so many obvious things to talk about the next 5-10 years of what is happening in the 'self driving' car area of technology and yet this study talks about things possibly happening 20 years from now. this study fails to mention. 1) insurance rates on people generally 2) car hacking 3) gps location tracking sharing and the implications of this 4) basic highway driving augmentation tech as it stands to be used NOW in volvo and a few other models. furthermore in the 'distant future' is is remarkeable the above study fails to mention perhaps the MOST important thing that will be affected PARKING PATTERNS. and then it fails to mention speeding tickets and the implications on the dramatic reduction in traffic police, fines, etc.... which implicates the FULL CONTROL, SOCIETY. where your vehicles don't afford you the choice to break rules.
Stephen N Russell
another issue is System Hacking by groups to disrupt trains & cars alone & whole system crashes unless autonomous cars have Built in cybersecurity factors alone Otherwise yes for the Pros,. alone
Norm Rhett
The assumption that occupants of a self-driving personal vehicle will expect train-like motion is not realistic. There is no good reason to get up and walk around in a moving car. If there were any change in expectation, it would be toward smoother, faster, and better coordinated motion than traffic currently exhibits. It's easy to tweak a model and, if necessary, change the assumptions until it produces newsworthy results.
Dave Brough
Why was it so important to replicate a 'rail-like' ride where half the passengers ride backward-facing and unrestrained, and thus would be thrown out of their seats with car-like acceleration? In a real-life car situation, occupants are belted in and facing forward, and in addition to the normal 2-second human lag, there are additional factors -- like putting the vehicle in gear (many people follow safety experts' advice and put their vehicle in park or neutral to avoid 'forward creep)'; many others are eating or putting on makeup; others are texting, and so on. The SDC 'suffers' none of those issues: Every vehicle in the queue would instantly accelerate, and using existing vehicle accelerations, would leave everything in its dust. This was a 'study' designed to have the SDC fail.