Thursday, August 26, 2010

Traffic "essay"

This is something I wrote in the comments section of:, which is a cool website about traffic theory written by a regular guy who has a bad commute. It was too long for the comments section so he had to break it up. :-)

I’ll say right up front that I probably fall into your category of “aggressive driver”, but that doesn’t mean I don’t analyze traffic patterns effectively or that I’m not a good driver. I do a TON of traffic pattern analysis on my daily 1.5 hour each way drive, and even though I regularly cruise comfortably at 85mph, I’m a very safe and courteous driver, or at least I try to be.

I find your website very interesting, and I will definitely admit that once a traffic jam has formed, your methods are a great way to help break up the jam and get the traffic moving again. I've started using it myself and will continue to experiment with it.

However, I also believe that some of the driving behaviors you're advocating could actually be responsible for *creating* traffic jams in the first place. I know that's a bold statement (especially on this site!) so let me explain what *I've* observed over years of commuting and experimentation. Hopefully people don’t dismiss it out of hand since it’s a bit of a contrary point of view.

I think there are TWO potential mindsets for creating smooth, efficient traffic flow, and this website is very biased towards one of them and against the other. My theory is that the issues arise when you mix drivers of different mindsets on the same roadway. I don’t know if there is any official descriptive word of the two mindsets, but I would characterize them as the “Progressive” group and the “Limiting” group. The “Progress” mindset prioritizes behaviors that allow for people to make as much progress as possible, and tries to *remove* limitations to the flow of traffic, and the “limiting” mindset tries to achieve smooth traffic flow by limiting traffic to achieve an “orderly flow”. So examples of “Progressive” behaviors that make traffic flow smoothly and quickly are things like always moving to the right, moving over whenever anyone approaches you from the rear, and not pulling into a lane on your left unless you can do it *without* causing anyone already in that lane to have to slow down before you get a chance to get back into the right lane (which you always do). “Limiting” mindset people would prefer that people avoid changing lanes whenever possible, that everyone travels at a steady average pace, and artificially slowing traffic to help remove the waves from traffic. I’m not saying either is “right” or “wrong”, and generally speaking if you have a population of cars on a roadway containing only one type or the other, you may not get a traffic jam at all. I think traffic jams result when you MIX the two different kinds of drivers on the same roadway, which causes both of them to get really frustrated. And as a side effect, they are both convinced that the other drivers have no idea what they are doing. :-) Just to illustrate the differences with a real life example, I think there are several places on this site where people advocate putting a “rolling roadblock” into traffic to slow everyone to a steady average pace, restoring orderly flow and increasing the “average” speed of traffic by reducing the start/stop affect of stop-and-go traffic. However I have also seen a similar increase in the overall number of cars to traverse a particular section of roadway when an ambulance or police vehicle goes through the left lane with their emergency lights on, clearing slow-moving vehicles out of their way as they go, and then a string of more aggressive drivers fill in that gap and maintain a higher rate of speed, which interestingly seems to also increase the speed of adjacent lanes because people start paying attention more closely when they see other people close by moving more smoothly and they aren’t. So having a faster-moving vehicle artificially break up the traffic jam by removing slower drivers from the left lanes *also* helps traffic flow.

So onto my observations. First of all, there isn't really any such thing as an "invisible wave" that creates traffic. If you look at ANY knot of traffic on the highway, nine times out of ten you'll see the same thing at the front of it - a Volvo, Hybrid (Prius, etc) or mini-ute (Toyo Rav4/Honda CRV) in the high speed lane with a line of cars behind them and empty space in front of them. After they create the traffic jam, they may end up moving on, but the wave stays in that spot and continues to live on with a life of its own.

I’m not profiling when I mention those three classes of cars - it’s based on observations, and it changes over time. (back in the early 90s, for example, the front car was likely to be a Ford Escort or Hyundai Excel, although if you watch carefully, Volvos are ALWAYS one of the top 3 cars guilty of starting jams) I have a theory for why it’s those cars, too, but that’s just my opinion. Basically when those cars are designed, handling and performance are very low on the list of design priorities, so the drivers of those cars FEEL like they are driving “plenty fast enough”, so they assume they are going fast enough for everyone else too. I had a girlfriend back in high school with a 1988 Hyundai Excel, and 55mph felt like breakneck speed in that pile of crap. I can honestly say my car feels safer at 90mph than that Excel felt at 55mph, and can probably stop from 90mph in less distance than the Excel could from 65. (14.5” brake rotors and very sticky tires)

These drivers at the front of traffic could and should move to the right, allowing traffic that wants to move faster to pass them, but they are either too discourteous, or more likely, completely oblivious to the fact that they are holding up the flow of traffic, so they just stay there and force traffic to pile up behind them. THAT ALONE is responsible for some large percentage of the creation of new jams.

Now when you say that creating a big space in front of you helps things, that is a logical statement in many different ways - especially from a reaction time and stopping distance perspective, but you are missing something psychological that is more important when it comes to traffic jam generation. When you have an oblivious driver (Volvo, etc)at the front of a pack of traffic, not moving over, they are going to stay there *forever* if you just stay 2 seconds behind them. Because again – in their eyes they are going PLENTY fast enough, and as long as nobody is riding their bumper, there is no evidence to the contrary. I'd say, based on my observations, that only about 10% of drivers in that situation (nobody on their tail) actually drive the way you SHOULD drive, which is you *always* change to the rightmost lane you can reach after each and every "pass".

Also important here is that probably another 15-20% of people will move over to the right if they see someone close in their rear view mirror, which is officially "tailgating", but is also an effectively method of conveying the fact that the front car is actually guilty of holding up traffic and is obligated to either move over to the right or speed up to match the speed of the person in front of them. I think that is the reason you see so much tailgating - it's people who have kept a safe distance for a while (maybe miles!) but the person in front of them is not a competent enough driver to know enough to move over, so they start easing up on their rear bumper to try to wake them up. And of course the 3rd car in the knot does the same thing, etc. Now not to pick on anyone, but if you’re one of those drivers who is trying to open up gaps in front of you, AND you’re doing this in the left lane, then it’s YOU who is starting traffic jams! Just move over and let people pass!

So basically I don’t think it’s the “aggressive” drivers who are creating the traffic jams in the first place – it’s the oblivious ones - the ones who are only interested in what is happening in front of them, and don't ever look in their rear view mirror and refuse to move over no matter what, even if you tailgate them or go around them on the right when you get enough free space. THOSE are the drivers who cause traffic jams. Some percentage of these people don't even have their rear view mirrors adjusted to SEE behind them! (if you look forward at their rear-view mirror and see their foreheads or necks, then how can they see what's going on behind them?!?)

So when I said before that the practices on this site might be contributing to *starting* traffic jams, this is what I was talking about. If people are sitting in the left lane and allowing spaces to build up in front of you while there is already a traffic jam and everything is locked up anyway, then fine, but don't ever do this while traffic is still moving or it's YOU who are starting the traffic jam. The car ahead of you will think their speed is fine since they are "pulling away from you", and so they won't move over, and the whole thing will propagate into a traffic jam.

I have actually seen some successful tactics to remove these people from the front of the pack, although it’s generally increasing your risk to use those tactics. Since they are only looking in front of them, sometimes passing this person on the right when you have enough space in the right lane (which will surely happen since they aren't moving over to the right as they should), and then *not* moving into the left lane after passing them on the right shows them that they are actually slowing down traffic, and if they are even halfway paying attention, they should then move over to the right. I call this the “lead by example”, because it should be *impossible* to pass a car on the right if the car on the left is following the simple driving rule “keep right except to pass” – if you can get by them on the right, then they obviously weren’t passing anyone and didn’t move to the right. I have seen some people on this site gloat that they ignore those "aggressive drivers" or "cheaters" going around them on the right, but what you SHOULD be doing is moving over to the right, because you're in the way of everyone behind you.

For some more oblivious drivers with tunnel vision, it takes changing back into the left lane directly in front of them ("Buzzing them")to wake them up into realizing that they are blocking traffic. Hopefully these drivers wake from their stupor, look around, and now see the line of cars behind them, triggering them to move over. This works a good 25% of the time.

Then there are the REALLY oblivious drivers who will just sit in the left lane no matter what happens around them (called “left lane bandits”), and they need some very special tactics to clear the passing lane. Basically if you change lanes to get in front of them, and then SLOW DOWN so that they start tail gating *you*, often they will get frustrated and actually move to the right now that you are unavoidably in their line of sight. Usually the 3rd person in line, who has been following the oblivious driver long enough to know that they are causing traffic, will then close the gap up to you quickly enough that the blocker can’t get back in, and the whole line of cars can now finally pass and make progress again. Now I can already hear a bunch of people saying “But that’s dangerous – you shouldn’t be passing on the right”, and I agree 100%, but this dangerous situation is caused by the SLOW person in the left lane, NOT by the more aggressive driver passing on the right. If the first driver would just move over and be courteous, then this situation wouldn’t have arisen in the first place. I have only done this a couple of times, but both times I literally got beeps of appreciation and hand waves/nods from the other drivers as they passed me (since I immediately pulled to the right when I was a few cars past the slow driver, in the next open space on the right) so they totally understood what I had done and appreciated it.

I would also like to comment on the statement that changing lanes doesn’t get you there any faster. When I drive, I observe things very carefully in terms of locating “landmarks” in each lane, and seeing how well each lane is moving. On some stretches of road, you can also focus way ahead of where you are and determine which lanes are GOING to be moving well once the traffic compression waves make their way back to you. For me, my observations are mainly focused on which lane to be in at certain points along the trip up Rt 95, since there seem to be traffic patterns that are relatively static from day to day, even though there are certainly exceptions due to external influences like breakdowns or construction.

The one thing I would say is that the assumption that "cheaters" or whatever you want to call them do not make it through traffic any faster than you do is definitely questionable. Again, I'm definitely on the more "aggressive" side of the equation, but very analytical, and I can definitely see on a daily basis, that I, *on average*, progress faster than other drivers who are just staying within their lanes. Yes, you can occasionally make a wrong choice and end up losing some ground, but if you recognize the normal patterns and know what lanes to be in where, you can *definitely* beat the average every time. I have proven this by driving with another car, with the same departure point and destination, and arriving 10 minutes earlier on a 1 hour drive. It’s hard to quantify or state a hard and fast rule, since there are so many factors to figure in, but *generally* speaking, if you are in wall to wall traffic, then the right lane will move slightly faster approaching an offramp, and slow down as you approach the onramp due to the cars coming on, so if you time it correctly, you can make up some ground and then move to the left lane and avoid the extra volume entering the highway.

Based on what you’ve written here, I now know that this may be creating additional traffic *behind*, but I’m just saying it definitely gets you where you’re going noticeably faster if you know the patterns and make the right strategic and tactical decisions. I think the mistaken assumption is that you don’t pick up that much time from maneuvers like this. Perhaps the *distance* measured in the number of cars you move forward in the line is low (say a dozen or two) so it’s not that much forward progress, but in terms of *time* it’s actually much more than you think because once you reach the front of the wave, you start moving again (say you get back up to 55mph) but people still trapped in the wave, even just a couple dozen cars back, are going to be sitting in that wave going on average 5mph for another couple of minutes before they can speed up. So by the time they get out, you are considerably farther along, and have had the opportunity to pick up even more spots if you know the patterns and what lane to be in. If you can get through *each* traffic wave 10 cars earlier than the average, that time definitely adds up as you’re spending less time trapped in each wave. Sure, 10 minutes isn’t much to gain, but it’s something and for a competitive person like myself, I can often find another similar driver and compete to see who makes the most progress. Generally speaking both of us are making much more progress than the average traffic, it’s just a matter of how much more.

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