Why do drivers swerve left to turn right (and vice versa)?

November 18, 2013 1:21 PM

I see this behavior all the time on the road, and I don't really get it: drivers about to turn -- usually into a parking lot/space -- who first swerve in the opposite direction before making the turn. Sometimes it's just a small movement. Other times the driver will actually swerve into the other lane before turning. What is the advantage in doing so? It doesn't look like a move that saves any amount of time or effort, and in most cases seems counter-productive. I've tried this to see what the benefit is, but have only ended up making my turn less efficient.
posted by Mo' Money Moe Bandy to Travel & Transportation (33 answers total)

It could conceivably help compensate for a large turning radius.
posted by ROU_Xenophobe at 1:23 PM on November 18, 2013 [7 favorites]

Besides the turning radius thing, you have to slow down more for sharp turns. Wider turns = can drive faster.
posted by chowflap at 1:25 PM on November 18, 2013

I do it to get a good, straight angle into a tight parking space.
posted by Ruthless Bunny at 1:26 PM on November 18, 2013 [39 favorites]

Turning radius. It's easier to get into a parking spot in particular from farther away.
posted by Etrigan at 1:26 PM on November 18, 2013 [1 favorite]

If it's a narrow spot there might not be a way to get straight in without adding some radius by swerving the wrong way, first.

I do think people tend to overexaggerate this; with that said, my driveway is just wide enough for a car (curbs on either side) and I cannot turn right into it without cutting left first. If I tried, the rear wheels would hit the curb.
posted by ftm at 1:26 PM on November 18, 2013

Yeah, turning radius. I used to do this when I had a truck, and the habit persisted for a while after I downsized to a car.
posted by TungstenChef at 1:27 PM on November 18, 2013

yeah, my car (ford escape) has a sucky turn radius and any extra swivel room helps
posted by changeling at 1:27 PM on November 18, 2013

Also if you spend a lot of time hauling a trailer, it becomes a habit to make all turns wide, because you have to do that to avoid taking things out with the trailer.
posted by HotToddy at 1:28 PM on November 18, 2013 [2 favorites]

This is necessary unless your car can make 90-degree turns like Automan's.
posted by Tanizaki at 1:29 PM on November 18, 2013 [5 favorites]

Its to get a wider turn radius, but you can get the same effect from just driving further away from the curb as well. In fact, swerving out so your car is not at a 90 deg angle from your intended driveway or road hurts your turn radius but you more than make up for it by getting further out away from the curb you are travelling parrallel to.

There is also a technique in rally racing that is called the Scandinavian flick. but this is not something one should be doing on the public streets.
posted by bartonlong at 1:30 PM on November 18, 2013

Response by poster: I'm having some trouble visualizing how this helps with a wide turning radius. I can see why it would help to move further away from your target, but wouldn't it make more sense to just drive at an angle away from it (within reason, of course) prior to the turn? What I usually see is something like a sharp little "?", which looks (to my eye) like it's actually making the turn more difficult by forcing you to make a tighter, more abrupt motion.
posted by Mo' Money Moe Bandy at 1:38 PM on November 18, 2013

If you are going to take the turn with your hand upside down on the wheel, your natural gesture is going to pull the wheel to the left as you grab it before you go hard over to the right. I think this may explain it in some cases.
posted by feloniousmonk at 1:40 PM on November 18, 2013

Yes that would make sense (assuming nothing else is in the way on the outside).

But people often don't plan ahead to that extent.

They're not trying to make the turn easier, anyway. They're trying not to clip the kerb or bash the van that's trying to get out of the side road they are turning into.
posted by emilyw at 1:41 PM on November 18, 2013 [4 favorites]

I can see why it would help to move further away from your target, but wouldn't it make more sense to just drive at an angle away from it (within reason, of course) prior to the turn?

My mindset on these things (and I do "question-mark turns" pretty much every day in my work parking garage) is that I drive on the right until I have a good reason not to, and I don't generally see the parking space until I'm too close to have drifted slowly over to the left lane, so the question-mark turn is as good as I can do.
posted by Etrigan at 1:42 PM on November 18, 2013 [3 favorites]

angle away from it (within reason, of course) prior to the turn?

I think that's the rub. How much driving in the opposing lane is "within reason"? I'd rather turn out to turn in than drive in the wrong lane.
posted by Admiral Haddock at 1:42 PM on November 18, 2013 [5 favorites]

When driving on the left side of the street from the right side of the car in the UK, I noticed that if I did not specifically do what you are suggesting, I would hit the curb when turning left. I tend to make a wider turn when turning right in the US, so I think it probably has to do with the bulk of the car being on the opposite side of the driver and needing to mentally compensate for that.

In some sense the turning axis is perceptually different if you are turning left or right but are seated as a driver on the opposite side of the turn.
posted by thorny at 2:00 PM on November 18, 2013

wouldn't it make more sense to just drive at an angle away from it

That'd be easier, but puts you in the oncoming traffic lane for a longer period of time, which isn't exactly a good habit to cultivate.
posted by ook at 2:11 PM on November 18, 2013

And when you're in a parking lot, driving too close to the parked cars on the opposite side of the space you're aiming for gives you less time to react if one of those cars suddenly starts backing up.
posted by rabbitrabbit at 2:13 PM on November 18, 2013

Best answer: People do this to avoid "cutting the corner." To illustrate: drive through a puddle, and then when you hit dry pavement, make a turn. Stop and get out of the car, and you'll see the tracks of the front wheels and the rear wheels. If you turned to the right, the track of the rear wheels will make a shallower arc that falls within the more curved arc of the front wheels.

This explains why, if you make a turn too close to the curb, the front wheels will clear it easily, but the inside rear wheel might clip the curb. Now, having said all that, if you just keep a sufficient distance between the side of the car and the curb (or the line of parked cars), you won't have to swerve out to achieve this. But, if you think you might be a little too close and want to make sure you don't clip the curb, or the car next to the empty parking space you want to pull into, the swerve can help that situation. But, there's really never a call to swerve so far that you veer into the lane of opposite traffic.
posted by fikri at 2:28 PM on November 18, 2013 [5 favorites]

Just an additional data point: parking lot requirements (where dictated by a local municipal code) typically have the same width for a drive aisle (the part between the parking spots that you drive down) regardless of whether there's parking on one or both sides, and whether the drive aisle is one-way or two-way, so the design assumption is that this type of thing is going to happen and the full width is required for maneuvering.
posted by LionIndex at 2:32 PM on November 18, 2013

If I'm driving down the lane in a parking lot, I'll stay to my side of the lane unless and until I actually find a space I want to pull into (or I'll stay toward the middle of the lane if it's a one-way sort of lot). Because the angles of most parking lots, I might not be aware of an empty space until I'm close to it. Then, let's say the space is on my right side, I might swerve left (after checking to make sure nobody is coming the other way or trying to pass on my left) to give myself enough room to pull into the space. If I didn't do that, I'd be too close to the space to get in, and would hit the car next my space if I tried.
posted by zachlipton at 2:34 PM on November 18, 2013

I generally prefer to left-turn into parking spaces for this reason.
posted by breakin' the law at 2:39 PM on November 18, 2013 [1 favorite]

I blame it on SUVs and other cars with terrible turning radii. My little hatchback has zero trouble turning into any parking place ever, but I think people who learned to drive on SUVs (pick-ups, minivans, etc.) may not realize that normal cars have the ability to turn into parking places easily, so even if they acquire a normal car, they keep driving silly.
posted by hydropsyche at 2:48 PM on November 18, 2013 [1 favorite]

People do this to avoid "cutting the corner."

Seconding this. I do this to avoid cutting the corner on the curb or to avoid hitting a post or other obstacle while pulling in. It's not a huge swerve, because I have a small car, but it makes me feel better about making sure I have enough room. Also, as zachlipton says, in parking lots where you might not see an empty space until you're pretty close to it and need to make that little swerve to fit into the spot without clipping someone's car. The only cars I see manage it in my office building's parking structure without swerving to the left a bit are the tiny cars like Fiats and Mini Coopers.
posted by yasaman at 2:52 PM on November 18, 2013 [1 favorite]

The optimum method of getting into a parking space without clipping neighbouring vehicles is, of course, backwards.

I'm surprised by people who find it easy to get into spaces forwards without pulling across first. Where I come from, often the other users of the car park have left me about a foot clearance on either side, and although my car is not colossal, I can't get in there in one go without either pulling across first or going in backwards. If the space is very narrow it's pretty much backwards or nothing.
posted by emilyw at 2:54 PM on November 18, 2013

Crude MSPaint drawing of getting a better angle when parking. Of course the correct method is actually to reverse in, the way the car pivots around the rear wheels makes it easier to line up.
posted by EndsOfInvention at 3:50 PM on November 18, 2013 [4 favorites]

I learned to do this when I moved to the suburban USA from London. It's a good way to easily drive into a space that's at 90° to you without cutting the corner and possibly hitting something like a post or another car. The alternative would be to reverse in, and Americans never reverse if they can avoid it, particularly around a corner.
posted by w0mbat at 5:08 PM on November 18, 2013 [1 favorite]

Another crude MSPaint drawing. The blue car making the hook never has to make a turn tighter than radius r1. The orange car still turns at radius r0 but it has a lot of extra time to fine tune because it squares up to the spot with more distance remaining.
posted by scose at 5:25 PM on November 18, 2013 [2 favorites]

But people do this outside of parking lots, while making ordinary turns, as if they are driving a horse and buggy.
posted by thelonius at 5:50 PM on November 18, 2013 [2 favorites]

To turn into a parking spot without weaving out I'd have to go really slow and turn my steering wheel quite a bit, changing hand positions a couple of times. Weaving out a bit means I don't have to slow down as much, but more importantly means I don't have to turn my steering wheel round and round.

So a right parking turn is: 1/2 turn left then 1/2 turn right (using right hand); then another 1/2 turn right then straighten up 1/2 turn left (using left hand). Not weaving out, I'd have to: 1/2 turn right (using left hand), cross right over left and another 1/2 turn right (using right hand), then about another 1/4-1/2 turn right (using left hand). Then reverse the procedure to straighten up.

Basically the no-weave-out turn takes a lot of hand changes and arm flailing about. The weave-out turn is one smooth motion where I don't actually have to take my hands off the wheel.

Side note: at least in my experience there are lots of 'head in only' parking restrictions in U.S. parking lots.
posted by zengargoyle at 6:41 PM on November 18, 2013

Just to do your head in, meet the hook turn. You actually turn right from the far left lane of traffic (well, in Melbourne, where we drive on the left). Mind you, this is mostly because of the trams and to allow traffic going straight to continue and not be held up by people waiting to turn, but it's still a reason why people do it!
posted by Athanassiel at 8:17 PM on November 18, 2013

The hook turn is the second most terrifying thing about becoming an Australian driver after driving as an American (the most terrifying thing is the first time you forget which lane you're supposed to be in while you're turning.)

The question-mark turn is definitely more pronounced in farming towns, because you have to do it at the end of every row when you're plowing.
posted by gingerest at 10:44 PM on November 18, 2013

I get the parking lot thing, but have to say this drives me crazy on four-lane roads when drivers in the adjacent lane swerve into mine. I've always chalked it up to living in NASCAR country.
posted by Shoggoth at 6:44 AM on November 19, 2013 [1 favorite]