Are we there yet?

Motorists could (should?) learn a thing or two from the ants

WITH more Americans than ever economising by driving, rather than flying, to visit friends and family the long, winding lines
of bumper-to-bumper traffic must have made more than a few turn around and miss the food and fun.
When stuck in traffic, it's interesting to note the way ants manage to avoid traffic jams.
The first thing you notice when you watch an ant trail is the way the convoy never comes to a halt, no matter how busy the traffic.

The ants don’t even slow down. As the traffic density builds at junctions where ant trails converge, they continue to maintain
the same steady speed as they do on quieter stretches. More intriguing still, they exhibit none of the mutual blocking
behaviour found on crowded roads—where motorists prevent others from squeezing in and, in so doing, hinder their own
progress as well.

There is a world of difference, of course, between ants genetically programmed over millions of years to follow pheromone
trails in the best interest of the colony, and motorists constrained to follow the rules of the road, yet determined to demonstrate
their free will and to maximise their personal gain. In short, for ants fetching food from a distant source, an efficient transport
system is essential for the colony’s survival. For motorists, it is merely a means to get from one place to another while
struggling to retain their freedom and individuality.

Yet, despite the differences there maybe lessons motorists can learn from the collective march of ants.

For one thing, there is a lot of communication going on between individual ants on a trail, as they broadcast their presence
and their intentions chemically to one another. That clearly helps them regulate their distance apart (headway).
In so doing, they maintain an optimum speed for a maximum volume of traffic.

One day cars will likewise be able to communicate with one another. It would be preferable if they did so without their
owners’ involvement, otherwise there would be even more scope for abuse than at present. However, given the interactive
cruise-control systems being incorporated into inter-vehicular communication equipment, it ought to be possible to
optimise the space between cars so they can collectively maintain the best speed for a maximum throughput of traffic.

Saying this is one thing; doing it is another. Over the past 50 years researchers have made little progress in developing
a general theory of traffic flow. That is because the whole messy business involves elements of behavioural psychology
as well as the laws of mechanics, control theory and fluid dynamics. In short, traffic patterns are invariably far too
complex to be modelled mathematically.

As a result, today’s traffic models rely heavily on empirical data from surveys and road sensors to plug the holes in the theory.
At best, they work only with the uninterrupted traffic flows found on motorways and the like. In America, the optimum density for
the best use of road space is around 50 vehicles per lane-mile. In other words, vehicles need a headway of around six lengths
for the traffic to flow smoothly.

If the traffic density increases much above that, the flow pattern begins to become unstable. Unlike convoys of ants,
road traffic behaves in a highly non-linear fashion. Even minor disturbances—caused by, say, a driver touching the
brakes a shade too hard—can then create ripples of slowing traffic spreading back upstream and bringing everything
ultimately to a halt. Such “phantom jams” occur when there is no obvious obstruction.

One of the latest suggestions is that such rippling disturbances are rather like shock waves spreading out from an explosion.
Mathematicians at the Massachusetts Institute of Technology call them “jamitons” and have used shock-wave theory to
help engineers minimise their impact on traffic.

Leaving aside roadworks, traffic jams are ultimately caused by drivers doing something stupid—taking unnecessary risks,
misjudging distances, over-estimating their own skill or simply driving too fast. Don’t expect that to change much.
In fact, as cars get safer, drivers seem to compensate by taking even bigger risks.

In a classic study done over a decade ago, Norwegian researchers looked at the way taxi drivers in Oslo behaved with
and without airbags and anti-skid braking systems fitted to their vehicles. Drivers with the better brakes tended to travel
closer to the vehicle ahead; those with airbags often failed to buckle their seat-belts.

The question that was never resolved was whether drivers respond more positively to measures that reduce accidents
(anti-skid brakes) or to those that reduce injuries (airbags). Researchers are still not sure which is better.
What they do know, though, is that technology aimed at improving safety does not always have the intended effect.
And, as other studies have shown, people drive more carefully—and have fewer accidents—when many of the safety
measures are removed.

So is the answer tougher traffic laws, rather than more safety engineering?
That’s a difficult one.
Here’s the conundrum: traffic laws are ostensibly there for road-users’ own safety; yet people flout them more than
any other laws of the land. Perhaps drivers do so because they perceive them to be concerned, first and foremost,
with allocating blame after an accident, rather than with helping prevent accidents happening in the first place.

There are other reasons as well. Having to comply with seat-belt rules, heed traffic signs and watch speed limits
all the time while driving means that traffic laws of one sort or another play a far bigger part in people’s daily lives
than any other set of rules. And because they are ubiquitous, the opportunity to violate them is far greater.

Compounding matters, many traffic laws can be broken just a little—say, driving a few miles per hour faster than
the speed limit, or rolling slowly past a stop sign instead of coming to a halt. With other laws, you either abide by
them completely or break them and suffer the consequences.

Motorists seem to feel they can violate traffic laws a little without damaging their self-image as law-abiding citizens.
That is why speeding violations, in particular, are the most common breaches of the law known to man
—and, for similar reasons, why traffic jams are a daily occurrence. Being a bit short of self-awareness and free will,
ants don’t have such problems. And they travel smarter as a result.