The Red Light Gambit

You’re approaching a red light on a three-lane street.  You are driving in the middle lane and have time to comfortably move to the lane on either side of you or simply stay in your current lane.   At the red light ahead you can see the types and numbers of vehicles in each lane but you can’t see the drivers occupying the cars.  For argument’s sake, let’s assume: 1) you’re an active driver (meaning you’ll change lanes to improve your odds of getting somewhere faster); 2) none of the vehicles will be turning at the light; and 3) the cars in front of you are the only other cars on the road.  Which lane do you choose?

Here is the breakdown of traffic ahead of you in each lane:

Left Lane: (1) Large Semi Truck (the length of 3 compact cars)

Middle Lane: (1) compact car, (1) sedan, and (1) sports car

Right Lane: (1) van and (1) SUV

Before we answer this, let’s digress for a moment:

The frustrating nature of driving anywhere at “peak times” is the sheer volume of other vehicles using the same major arteries at the same time.

When I first started driving, I naively thought a few slower drivers somewhere ahead of me were causing traffic to slow.   The reality is a bit more scientific.  Traffic hinges on the total physical mass of objects passing through a constrained space.   Image the difference of running a shower vs. running a bath.  Even with the drain fully open, if you have enough water pressure, the bath water will start to accumulate while the shower water tends not to build up.  This generally occurs because the per-second volume of water produced by your showerhead is lower than the per-second volume of water produced by your bath spout.

However, what happens if you have exactly the correct number of cars on the road such that there are no volume constraints.  Let’s further say that these vehicles are all travelling at exactly the same speed.   The answer: You would eventually get waves of traffic slow downs.  Strangely (or perhaps not so strangely), computer piloted vehicles would have no problem staying at the speed constant and would not force traffic waves.  However, as soon as you put humans behind the wheel, traffic waves will ensue.


The individual driver is only certain of what she is doing currently and what she intends to do next.  There is no way to know what other drivers intend to do.  As a result, the individual must create a safety barrier to facilitate reaction time.  In the case of the previously mention scenario in which there were no volume constraints, this “safety barrier” cascades throughout the lines of vehicles and ultimately forces slow downs.

Tack on the capacity constraints (more vehicles than space on the road) and you will always have traffic issues.  The capacity challenges are sometimes addressed by impacting the volume of cars accessing a main thoroughfare.  You can see this each time you get stopped at a freeway entrance by a traffic metering light.  Otherwise, we are at the mercy of the safety barriers that fellow drivers ahead of us create for themselves.

How do you resolve the safety barrier issue?  Fully networked autopilot cars continuously directed by an overarching system.  Simply enter your destination and let the car navigate and drive while it silently interacts with all of the other cars on the road to streamline speed, lane changes, safety, etc.   Obviously this won’t happen anytime soon so let’s return to the traffic light question:

The light is still red, which lane do you choose?

The answer:

The left lane (with the large truck).


With all other elements constant, there is only one human being ahead of you in the left lane.  Even though that human being is driving a slow moving truck (the length of three cars), your odds of getting through the light faster are improved.  One driver means only one safety barrier (the one you create between your car and the truck ahead).  It also means a lower likelihood for the person in front of you to be distracted and not hit the gas as soon as the light changes.

What does this all mean?

Ultimately you, the individual driver, are responsible for traffic issues.  Pay attention and keep up with the person in front of you… or simply stay off of the road!