The solution to our traffic problems is already here

Thursday, 12 July 2018

The technology to reduce phantom traffic jams already exists and is in a lot of late model cars.

There is possibly nothing more frustrating than spending ages stuck in a slowly crawling queue of traffic only for it to clear with no discernable reason for its existence in the first place.

This is a phantom traffic jam. City drivers know all about them.

'You keep on saying, 'There must be an accident, or construction or something,'' said Massachusetts Institute of Technology (MIT) computer science professor Berthold Horn in a recent interview with LiveScience.com. 'And then you drive and drive and drive … and there isn't anything there.'

Ever been stuck in traffic for no obvious reason? That would be a phantom traffic jam then.

A phantom traffic jam begins when a car in heavy traffic slows down slightly, causing the car behind to slow down slightly more - a process that is repeated and magnified as it spreads backward through the lane of traffic like a wave, getting worse as it goes.

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Without ACC, traffic would regularly grind to a halt in the test simulations.

In the LiveScience.com interview Horn said that phantom traffic jams were an 'emergent property' of the flow of vehicles down a highway. Eventually, the cars far behind are forced to stop completely or risk hitting the slower vehicles ahead and so the traffic grinds to a halt over literally nothing.

Horn says he has been working on the problem of phantom traffic jams for years, and he has come up with a solution: don't tailgate.

With all cars using ACC in Ford's test, traffic flowed freely, with little slow down and no stoppages.

This may not have seemed to be a solution that should have taken years of research to come up with, but by splitting the difference between the cars in front and the cars behind, the spacing of cars in a stream of traffic can act as a damper on phantom traffic jams.

In other words, keeping your car halfway between the car in front and the car behind can prevent the slow-down effect from being amplified by the cars throughout the line of traffic.

The latest ACC systems also work in tandem with steering assist systems.

But that relies on everyone in the line doing it, and Kiwis just don't do this, so that is where technology comes in. And it is technology that is already here, is actually quite common and if you have a relatively new car, you probably even have it. It is adaptive cruise control (ACC).

Adaptive cruise control works by using sensors - usually radar, laser, stereo cameras or a combination of all three - to maintain a constant gap to the car in front, regardless of its speed. Most modern systems work right down to a standstill and up to a speed set by the driver (that is never over the legal limit, of course, although most will work up to around 180-200kmh), with the most advanced systems also using sensors to take into account things such as steering angle when accelerating.

ACC is technically considered 'Level 1' autonomous technology, in that it does not provide full autonomy, only providing some help to the driver, but does not completely drive the car by itself.

As a part of its research into its next-generation driver-assist technologies, Ford and the Vanderbilt University in the USA recently conducted a large-scale test on the effects of ACC in eliminating phantom traffic jams, using three lanes of 12 vehicles each on a high-speed oval simulating motorway conditions, with illuminating results.

The lead vehicles in each lane slowed from 96kmh to 64kmh to mimic a traffic disturbance. Without ACC technology drivers amplified the initial braking event, in some cases to the point where traffic slowed to a crawl.

The test was then repeated with all vehicles using ACC, which outperformed the human drivers in almost every braking situation. In one run, the ACC actually suppressed the braking wave so much that the last car in the lane only slowed by 8kmh instead of coming to a standstill.

'This demonstration was a unique opportunity to understand how commercially available active driver-assist technologies can be used to positively influence traffic flow,' said Daniel Work, civil engineering professor at Vanderbilt University in the USA.

Work and lead PhD researcher, Raphael Stern, have been working with the support of the US National Science Foundation to determine how smart technologies can provide a pathway to fewer traffic snarls – and reduced overall fuel consumption. They plan on publishing the results of the Ford test in an upcoming academic journal.

'The fact that we saw a commercially-viable ACC system fully suppress the traffic backup is quite impressive,' Work said. 'And while we know this won't happen in every situation or in every circumstance, it's very promising to see that commercially available ACC systems can already have a desired effect in normal, everyday driving scenarios.'

The team also reduced the number of ACC active vehicles to 33 per cent - the low threshold researchers have long believed could help suppress phantom traffic backups - with similar results to the full ACC tests.

Given that early forms of ACC first started appearing in the early 1990s and started filtering down into mainstream cars in the early 2000s, a figure of around 33 per cent of cars in Auckland having some form of ACC isn't wildly outside the realms of possibility.

The technology has started making its way down into lower priced cars, with the likes of Suzuki's popular Swift getting it on some models.

However, according to Work, while the automated systems can function with greater consistency, humans still have one big advantage over the machine systems: their ability to see one or more vehicles ahead, which enables them to be more precise in their response to traffic slow-downs.

'The big takeaway from all of this is it's to everyone's benefit to practice good driving. Give ample space between you and the vehicle ahead, stay alert and that will always help traffic flow more smoothly, and help us all get to our destinations on time,' Kane said.

So it would seem the solution to at least some of our traffic woes is obvious - drive smoothly, don't tailgate and, if your car has it, use the adaptive cruise control.