Cognitive Daily

Casual Fridays: Driving like maniacs

Last week’s Casual Friday survey asked readers to describe how they expect other drivers to behave when merging onto the freeway. Now that the survey has been completed, I can let you in on a bit more of the observations that motivated the survey. I live in North Carolina, and I like to visit the big cities on the East coast, especially Washington and New York. This means I’ve done a lot of driving through Virginia, and I thought I’d noticed a peculiarity about Virginia drivers. In Virginia, it seemed to me, like no place else, the other drivers always expect you to get out of the way when they’re merging onto the freeway. Sometimes it seems as if they don’t even look to see if anyone’s coming before they barge out into traffic.

But perhaps these incidents become exaggerated in my memory, and Virginia drivers aren’t any better or worse than they are anywhere else. Now we have a chance to find out: we’ve again maxed out our survey engine, with 250 responses. I was hoping for a broader geographic distribution of response than we achieved: just 16.4 percent of respondents came from outside of North America. This contrasts to a sampling of 100 readers from our stats page this morning, where around 50 percent of visitors came from outside the U.S.

Possible explanations: people in other countries don’t drive as much as Americans, or, since the survey was posted late Friday afternoon in the U.S. — already late evening in Europe — our response was skewed to North America (as I write this, at around 2 p.m. Eastern time, over 80 percent of recent visitors come from North America).

Nonetheless, because of the large sample size, we were able to attain significant results. Let’s have a look at the numbers! The first question was intended to test the “Virginia hypothesis” — the idea that certain drivers expect the people on the highway to get out of their way, rather than seeking to modify their own driving behavior to adapt to driving conditions. Here’s a summary of the responses:

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The largest portion of drivers, whether in North America or in the rest of the world, expect the drivers on the highway to maintain their current speed. While a greater portion of North Americans expect other drivers to change lanes than non-North Americans, this difference wasn’t significant. However, significantly more non-North Americans expect others on the highway to slow down for mergers compared to North Americans.

Now, what about when a driver is on the highway and others are merging. How do drivers expect mergers to behave?

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Overwhelmingly, freeway drivers expect the people who are merging to slow down in order to merge. (This question also generated my favorite “other” response: “Some essentially random action.” 14 respondents offered a pair of responses that perplexed me: they expect people who are merging to slow down, and they also expect people who are already on the freeway to slow down. How does that work? Does everyone eventually end up standing still?)

This is fascinating stuff, but I still haven’t found a statistically significant confirmation of the Virginia hypothesis. Next I took a look at population density. There weren’t any significant differences between urban and suburban areas, so I combined that data and compared it to rural areas:

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Here we have solid evidence suggesting that the behavior I noticed is not confined merely to Virginia: A whopping 58.1 percent of rural drivers say they expect others to change lanes to get out of their way when they are merging onto the freeway, compared to just 26.3 percent of urban and suburban drivers. What I was thinking of as a Virginia effect is really a rural effect. And when I think about my drive from Charlotte to either Washington D.C. or New York, I have to admit that nearly all of the rural sections of that drive are in Virginia. There really isn’t any rural section of the drive on Interstate 95 from Washington to New York.

So are there any differences in how rural and urban / suburban drivers expect others to merge? Here are those results:

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Here, as with the overall results, most drivers expect the person merging to slow down, and there are no significant differences between rural drivers and urban / suburban drivers. But one “other” comment from a rural may explain this discrepancy: “I don’t ever recall having seen this happen.” Perhaps rural drivers simply don’t expect there to be a case when they can’t get out of the way of merging traffic, so they believe that if such a situation ever occured, the merging traffic would just slow down. This would be consistent with my experience driving through rural areas, where most drivers who are merging appear to assume that the drivers on the highway will just get out of their way.

Are these results consistent with your driving experiences? Do you have any other questions about the data, or alternative explanations? Let us know in the comments.

The next Casual Friday study will appear later this afternoon.

Comments

  1. #1 Gerry L
    February 3, 2006

    Hmmm. You seem to have left out an option. When I am merging, I adjust my speed (slow down OR speed up) depending on what is needed to blend into traffic. As far as what I expect others to do — it’s best not to have expectations; you’ll just be disappointed.

  2. #2 Bill King
    February 4, 2006

    Most astounding is your apparent presumption that thru trafffic should not yield the right lane. Yet, that is precisely what safe driving habits dictate and what I was instructed by state licensing officials.

  3. #3 Dave Munger
    February 4, 2006

    Bill,

    I’ll give you my opinion on the matter, but I should point out that it’s not backed up by any research other than my own driving experience and recollections of driving school.

    Thru traffic should not yield to merging traffic; merging traffic should yield to thru traffic. By yield I mean that merging traffic should assume that thru traffic has the right of way. If there is no place for the merging traffic to safely merge, the merging traffic should not assume that thru traffic will slow down. Why? Because thru traffic has the right of way, and therefore if anyone should be slowing down, it’s the merging traffic. If both cars slow at the same time, then the problem only compounds.

    However, merging traffic should not ever stop in the merging lane, because other merging traffic behind them is looking for a space to merge, not ahead. The chances of a rear-end collision are too high. It’s much safer to continue on to the shoulder than to stop in the merging lane.

    This is not to say that traffic on the freeway shouldn’t try to get out of the way of merging traffic if possible — they should, and this makes things safer for everyone. But if it’s unsafe for freeway traffic to get out of the way, they should not slow down — it’s the job of the merging traffic to adjust speed in order to safely merge.

  4. #4 Gordon Worley
    February 5, 2006

    When I took the survey I answered under the assumption that “expected” behavior meant not what I expected to happen, but rather what we expect of other drivers, i.e. I took them as ought questions rather than description questions. But hopefully not enough people made my mistake.

  5. #5 Mark Christal
    February 8, 2006

    I thought there should be some kind of Gricean “Cooperative Principle” in traffic merging and lane changing. This principal seems to be born out by your research that goes something like this:

    1. The merger should signal his/her intention to merge to drivers in the other lane.
    2. On seeing this intention, drivers in the merge lane slow down to open up space for the merger.
    3. The merger, seeing this appropriate response to the signal speeds up into the space to keep the traffic flowing. (Also, the merger doesn’t want to have the cars in the merge lane closing in on his/her rear after the merge.)

    There seems to be a tendency in the DC area for people to tailgate, making it tough to find space to merge into. I want a bumper sticker that says “Merge and Let Merge”.

  6. #6 ToddZ
    March 9, 2006

    Gerry L. and Bill King have it right. Merging traffic should be concerned with matching speed of thru traffic, not timidly waiting for an opening. Thru traffic should move over or adjust speed to create the space to accomodate them. Apparently Virginia drivers understand this.

    It is easier and safer for thru traffic, with their advance view of the situation, to move or slightly decelerate to let mergers in than it is for mergers to be looking over their shoulder while accelerating — then slowing down and — what? Stop and wait for an opening, then hit it like a drag racer?

    The worst result of this thinking is the petrified merger who stops on the on-ramp, afraid to get into the traffic flow until the right lane is clear to the horizon. If there’s any traffic, the right lane is not likely to spontaneously empty itself a half-mile back in anticipation of a skittish driver who must now accelerate from a stop instead of smoothly merging at the flow speed.

    This is the whole point of on-ramps. They give you space to accelerate to match traffic. If we were supposed to wait our turn to get on the freeway, they’d just make 90-degree intersections.

    Of course merging drivers need to actively avoid collisions, but the thru drivers in the right lane who refuse to budge, as if the road ahead is their birthright, are WRONG — and are contributing to congestion and hazardous conditions.

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