|
|
Socrates
and Leadfoot
Written July 7, 2007
LEADFOOT
Pittsburgh drivers are stupid.
SOCRATES
That's a rather strong statement for so early in the day, my
friend. Why accuse your neighbors of stupidity?
L
They're bad drivers. They don't know how to drive.
They even slow down to go through the tunnels!
S
Tunnels? Are there many tunnels in Pittsburgh?
L
Several. I'm talking mostly about the Fort Pitt and Squirrel
Hill tunnels. They're on expressways on the way into the city,
where the road takes a shortcut underneath the hills rather than
going around them.
S
Does it not seem reasonable that when you drive your car beneath a
mountain, you ought to reduce your speed?
L
There's no need to! The road's just as good inside the tunnel
as it is outside.
S
Then why do Pittsburghers slow down, do you suppose?
L
Beats me. They must be claustrophobic or something.
They're afraid of the enclosed space. Or maybe they're nervous
about going into the dark.
S
But you yourself don't get nervous?
L
Of course not. I don't let up on the accelerator unless I have
a good reason.
S
That's a prudent policy, isn't it?
L
And I don't complain about something unless I have a good reason.
S
Also commendable. But you're complaining today.
Therefore, would I be correct in assuming that you must have been
delayed at a tunnel recently? Perhaps this morning?
L
I sure was. The Squirrel Hill tunnel on the Parkway East.
S
So this morning you were driving on the Parkway the
above-ground portion and then you arrived at the tunnel, correct?
L
That's right.
S
Before you reached the tunnel, how fast were you going?
L
About 60 miles an hour.
S
And how fast did you go through the tunnel?
L
Only about 40.
S
Hmm. Let me understand this. You were doing 60, and then
you reached the tunnel and slowed down to 40?
L
Right.
S
Eureka! I think we have found the problem! Don't you see?
L
See what?
S
Are not you the bad driver?
L
Huh?
S
You slowed down at the tunnel! Is that not precisely
what you've accused the other drivers of doing?
L
But I had no choice! If I hadn't taken my foot off the gas, I
would have rammed into the back of the SUV ahead of me.
S
The vehicle ahead of you slowed down to 40?
L
Yes, so I had to do the same.
S
Eureka! I think we have found the problem! The bad
driver is that guy in front of you! You didn't happen to
get his license plate number, did you?
L
Well, no. But he wasn't alone. Everybody ahead of
me was slowing down.
S
Everybody? Whether they wanted to or not?
L
Right.
S
And why do you suppose they did that?
L
Because Pittsburgh drivers are stupid.
S
All of them?
L
Apparently.
S
Are you saying that all drivers except you are bad drivers?
L
They sure seem to be. They could go 60 before; why couldn't
they just keep going at the same speed through the tunnel?
S
Well, it does seem to be a mystery. Let's see if we can solve
it. Tell me, was there a lot of traffic on the Parkway this morning?
L
There always is.
S
Hmm. And does any of that traffic enter or leave the highway
near the tunnel?
L
Sure. There's an interchange just before it, and there's
another one after it.
S
So some of the vehicles around you were trying to change lanes to
reach an off-ramp?
L
Right. And there were even more cars coming onto the
Parkway there.
S
Were any of them merging into the lane you were using?
L
Sure. They have to. Once you get inside the tunnel,
there's only two lanes in each direction.
S
Interesting. Perhaps that gives us a clue. Would you
mind if I led you through a little thought experiment?
L
A what?
S
A couple of thought experiments, actually. Are you with me?
L
I suppose so.
S
All right, here's Experiment One. This one will be easy.
Let's imagine that you're driving down the Parkway at the head of a
line of five cars. They're all driven by members of your
family. Your wife is in the car behind you, then her brother,
then her sister, and finally her cousin. Okay?
L
Fine. Yeah, keep my wife's cousin as far away from me as
possible. He's a real idiot.
S
Let's also imagine that traffic is light today, so your little group
has spread out over a stretch of highway a mile long. Your wife
is a quarter mile behind you, her brother is a quarter mile behind
her, and so on. And all of you are going 60 miles an hour.
Got that?
L
Got it. No traffic; must be a Sunday morning.
S
As I said, you're driving the lead car, and you're approaching the
tunnel when a pickup truck pulls onto the highway in front of
you. Is he also doing 60 miles an hour?
L
Not right away, I suppose. He has to accelerate up to speed.
S
Correct. But you find yourself only a hundred feet behind him
and closing fast. Do you continue to drive 60?
L
Well, I'm not going to rear-end him. I'll either swerve into
the other lane or hit the brakes, I guess.
S
Let's say you slow down, but not very much. By the time you
get down to 57 miles per hour, you're no longer closing in on his
tailgate, because he's picking up speed. Both of you can now
accelerate up to 60 again, correct?
L
Right. It's just a temporary slowdown.
S
Now remember your wife, a quarter mile behind you. She sees
your brake lights come on. Does she also slam on her brakes?
L
I doubt it. She's got all that room in front of her, so she
keeps on coming, but she never gets close to me.
S
Very good. And her relatives behind her at quarter-mile
intervals don't have to slow down either, do they?
L
Of course not.
S
So all of you sail through the tunnel at 60 miles per hour, correct?
L
Correct. That's the way it should be.
S
But now let's consider the way it is. May we move on to
Experiment Two?
L
You're the professor.
S
This is a little more complicated. This time, it isn't Sunday
morning. You and your wife and her relatives are not spread out
over a mile. You're much closer together, the way you would be
in everyday traffic. How close would you say your wife normally
follows the car ahead of her?
L
Oh, I don't know. She drives like anyone else. Maybe
fifty feet.
S
You're probably right, but at that speed, you're supposed to allow
twice as much distance. Did you know that?
L
Those rules come from the bureaucrats. Or the insurance
companies. No one pays any attention to them, except some timid
old geezers who shouldn't be out on the highway anyway.
S
If you say so. Anyway, this time, when the pickup enters the
Parkway in front of you and you slow down from 60 to 57, your wife is
in her usual position fifty feet behind you. Does she slow down too?
L
I guess she'd have to, or she'd run into me.
S
When does she slow down? Right away?
L
Sure. She doesn't have a lot of time to think about it.
S
But she does have to notice that you've hit your brakes, and she
does have to decide that she ought to hit her brakes, and she
does have to move her foot from the accelerator to the brake
pedal. Doesn't all this take a fraction of a second?
L
Well, yes, there's reaction time, I guess.
S
So by the time she actually starts to slow down, is she still fifty
feet behind you?
L
She's closer than that.
S
Let's say twenty feet, okay?
L
Whatever.
S
And you've slowed down to 57. Does she also slow down to 57?
L
Naturally.
S
But she's only twenty feet from your back bumper. Won't she
feel that's she's too close?
L
I suppose.
S
Won't she want to slow down a little more, to put a little more
space between your car and hers?
L
All right, so she slows down a little more. She gets down to
55 and lets me pull away from her a little bit. But it's only
for a moment, because I'm going to be getting back on the gas, and
then she can too.
S
True. But before that happens, let's consider her brother in
the next car back. He sees his sister hit her brakes and slow
down to 55. He comes up right behind her. He has to hit his
brakes as well. He finds himself only twenty feet from her
back bumper. So he has to slow down not just to 55, but to 53,
does he not?
L
I suppose.
S
And the fourth car in line has to slow to 51, and the fifth car to
49. Do you see what's happening?
L
It appears that my little tap on the brakes is getting
magnified. I had to reduce my speed by three miles an hour, but
my wife's idiot cousin in the fifth car has to slow down by eleven.
S
That's right. And by the time he does slow down, you're
already back up to speed, aren't you?
L
I'm doing 60 again, but my relatives are all bunched up.
S
So can a disturbance in the traffic flow last longer than the
initial disruption?
L
I guess. It's like when there's an accident. The cops
clear the wrecked cars away, but traffic is still backed up an hour
later even though all the lanes are open.
S
Now think back to Experiment One. You were the only driver who
hit his brakes. Everybody else maintained their speed.
But in Experiment Two, your relatives do have to slow down.
What has changed?
L
Our cars are closer to each other.
S
And why are they closer together?
L
Traffic is heavier. There's not as much free space.
S
So when your wife's cousin, at the back of the line, slowed down to
49 miles per hour, was it because he was afraid of entering the tunnel?
L
Well, he is kind of a wimp, but I guess that's probably not the
reason he slowed down. It was because the rest of us were
bunching up in front of him.
S
Therefore, what can we conclude is the true source of your complaint?
L
I used to blame other drivers for being too nervous to go
into a tunnel at full speed.
S
And now?
L
I guess they're just too numerous to go in at full speed.
S
It's simple when you think about it, isn't it?
|
Remember,
you aren't IN tunnel traffic. You ARE tunnel traffic. |
|
|