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A PHYSICIST WRITES . . .
(June 2011)
I do believe this is the 90th column that I’ve composed for these pages [in the Thames Valley Group Newsletter] — at a rate, somehow, of ten a year. But how do you react to the notion that if and when my 190th column appears, you could be reading it (either on paper or on a screen) at the wheel of your car in the course of a journey? For that matter, I could be writing it while on the road to somewhere, just occasionally glancing up (for inspiration) at the traffic passing by. I’m talking about real cruise control here, with both your speed and your steering being managed automatically.
You may recall the item about this, headed “Road Train Passes First Test”, in the Advanced Driving magazine. It was actually a press release from SARTRE, which stands for Safe Road Trains for the Environment, an EU-funded organization. The ‘trains’ will be convoys, assembled on the move, and each led by a specially trained lorry or coach driver whose own vehicle is in automatic radio contact with the others (which can be a mixture of large and small) and controlling their progress and their separation.
The idea is that while driving along you may receive a signal that you’re near to an existing convoy. You can then reply with a request to join it. Having done so, then miles ahead when its route is about to diverge from yours, you tell the system to give back control of your car, and on you go.
While you were part of the train, you were relaxing and making better use of fuel and road space. The scheme could be operational (somewhere unspecified) in ten years’ time. The ‘first test’ just passed was a demonstration in Sweden of a single car being led and controlled by a lorry.
Well! You can probably guess some of the questions that went through my mind: how long might a train be? How will the speeds all along it be kept stable? Would I want to be sandwiched tight between two lorries whose drivers are both just sitting reading the paper?
And suppose radio contact was lost? What if someone ran out of fuel, or there was an accident? Will my writing stay legible, if the steering wheel is twitching under my pad of paper all the time? Will I be permitted to doze off? I investigated by taking a look first at the SARTRE website (click here) and then at some papers they’ve published, which report the research work to date and the plans for setting up and running the road-train scheme properly.
The planners decided early on that the convoys will operate only on motorways (or their equivalent) and without requiring any fixed roadside installations. To participate, your car obviously will need to have automatic gears, and to be fitted with distance sensors and the necessary mechanical and electronic equipment for operating the steering, accelerator and brakes while you are relaxing. And there must be a safe and easy way for you yourself to communicate with the ‘system’, when signalling to join or leave the convoy.
As for the overall control of the vehicles in it, this relies partly on all their sensors and partly on the actions of the leading driver. The latter are transmitted instantly to the rest of the train, so preventing the traffic-flow instabilities you would get if each vehicle simply responded to the behaviour of the one in front (as happens now with individual drivers in normal traffic!).
That answers one of my questions above — and some others are easily dealt with too: the maximum number of followers will be about 15, as driving-simulator tests showed that trains longer than this are difficult for overtaking drivers to cope with, especially if they intending to leave at an exit not far ahead. Heavy vehicles in a convoy will be placed in front of the cars, never behind them.
There will of course have to be a back-up means of communication between all the vehicles. And if anything disturbs their smooth progress, the system will be programmed with various procedures for responding safely. The argument put by SARTRE is that as most accidents now are caused by driver error, being in a road train with a professional lead-driver is inherently safer than driving ‘independently’.
Other benefits for you will include better fuel economy. This comes firstly from travelling at a steady speed with a minimum of braking, and secondly from the aerodynamic advantage of being close to the vehicle in front. But too close for comfort? This concern was investigated in further simulator tests. Drivers were shown a view of the rear of a lorry that they were slowly catching up with, and were told to press a button when they felt uncomfortable, and then again when they thought they were in danger.
On average, the (apparent) separations ahead at each button-press were around 15 m and 7 m respectively. Though when the participants were asked if a 10 m gap was adequate, most said yes. So as the current target for road trains is indeed a ten metre separation (in order to achieve good levels of safety and fuel economy), the hope is that drivers will trust the system with this gap, maybe after experience and some training. Also, most of the subjects did say that they would be happy to be ‘convoyed’ at speeds up to about 55 mph.
There was much more detail in what I read, but not a lot about the costs involved: surely you will have to pay first for the on-board equipment, and then again each time you join a road train? And I’m still curious about whether I can take a nap, once safely in line (or must I stay awake and be ready to drive again at any moment?). You see, the thought that my view of the road ahead will be totally blocked by a heavy the whole time is so depressing that I know I shall want to close my eyes — column or no column to write!
Peter Soul
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