jack

Every so often I hear someone talking about modelling traffic jams as waves travelling in a queue of cars. After some thought, I came to some tentative conclusions, without having actually tried any modelling or anything.

Imagine a long long stream of cars along a somewhat congested motorway without much overtaking.

The first observation is, whatever you do, you can't really affect the car in front as long as you're driving legally/safely. And whatever you do, you don't end up significantly behind them: if there's any sort of traffic, the average speed is much under the fastest speed you could drive in an empty road, so you can always catch up with them. So whatever you do, *you* will reach your final turnoff shortly after the car in front.

However, over a long run of cars, it seems plausible (I haven't double-checked the maths) that cars driving at 30mph have a greater throughput than ones alternating 60mph and 0mph, mostly due to needing more than twice the distance between at 60 than at 30. That means that if traffic is dense, there's a natural tendency for small disruptions to sometimes get magnified, when each car reacts a little slowly to the car in front, and hence makes a slightly larger correction. Whereas if you go a bit slower and give yourself a bit of extra space when the traffic in front of you starts of but you suspect it's more stop-start, hopefully the traffic behind you will experience *less* disruption.

I'm not sure, does that sound right?

Crossposts: http://cartesiandaemon.livejournal.com/1023918.html

For a while, I've noticed cars flashing both indicators simultaneously (presumably by turning hazard lights on then off again) to say "thank you" for letting them in.

I think I first noticed it by lorries -- google suggests it may have been a lorry driver custom first.

I really like the idea of being able to say "thank you" or "sorry" as well as "please" or "get out of my way" when driving.

Am I right that it's new, or did I just not notice when I started driving?

Presumably it's not allowed (just like flashing headlights to say "excuse me" or "after you" or "do you know your lights are on/there's something wrong with your car/etc" was never an authorised use according to the highway code). Is it a bad idea, or not?

Crossposts: http://cartesiandaemon.livejournal.com/864747.html

I don't normally drive into town if I can help it, I'll cycle.

That means that for the longest time I assumed there was no point even trying to park anywhere remotely close to the centre of town. I slowly realised that when people talked about how difficult it was, that was normally difficult compared to "driving up to the place you want to go and parking on the street right outside" -- it never occurred to me you might ever be able to do that unless you'd specifically checked in advance.

But over time I got used to knowing where I could park if I did want to drive.

However, I still wondered a couple of things.

Q1. In the evening I sometimes park on regent terrace (along the side of parker's piece) which has restricted parking before 6.30. However, I often meet friends at 6.30, and I always wonder what my chances of getting away with it if I leave five minutes before are.

Q2. If you park somewhere with a pay and display meter, are you legally entitled to leave the car long enough to buy a ticket? I mean, obviously everyone does, but do you actually have any protection if someone runs up and fines your car while you're buying a ticket?

Crossposts: http://cartesiandaemon.livejournal.com/804707.html

On Monday, I had my first parking violation :( I parked outside Liv's house on Sunday, and forgot that the resident's restrictions were "Monday to Friday" not "Monday to Friday excluding bank holidays". (Liv did too, but I never park somewhere based on a passenger's opinion, I always decide for myself if it's ok. So there's not much blame to go around, but none of it goes to Liv, except for happening to be there :))

On the one hand, I feel really stupid. The little voice in my head says "Bad citizen! You're an entitled elitist jerk who thinks laws are for other people. This is the first step on the road to careering down the wrong side of the motorway drunk off your head". On the other hand, the little voice in my head is always complaining about something, and it complains much louder about things that are embarrassing than things that are actually bad.

I tend to lump together "things I shouldn't do", but that means I blur the distinctions between "minor indiscretion" and "really bad things", and then have to work out from scratch whether it really matters or not. Because honestly, it turns out, they don't tow your car away or give you points on your license for a first offence, nor is anyone hurt. In fact, it seems that doesn't happen on ANY offence, if you keep paying the fines, so if you're rich enough, you can just park wherever you want. I could have hurt someone, I could have damaged my car or someone else's, I could have got points on my license. But actually, I just got a small fine that's basically inconsequential to me.

And I'm actually rather glad that my first fuck-up came at a time when I was fairly relaxed, I had a comforting Liv in the car to reassure me, and I could forget about it. Now I needn't really worry about it. And as atriec pointed out once, money given to the government isn't wasted, but is spent on useful things, so so much the better.

PS. Although I'm not sure if it's sorted. I paid the fine on the stoke.gov.uk website. Experimentation says there's an error if you enter a made-up reference number instead of the correct one, which suggests I entered it correctly. But they're not competent enough to offer either (a) any advice which of the three letter acronyms on the ticket corresponds to the "reference number" field on the webform or (b) any confirmation of the details of the ticket when you enter the reference number, so you're sure it's recorded correctly. So I _think_ I've paid, but it's also possible the stoke website just eats any money you send it but doesn't actually pay off the fines..?

Crossposts: http://cartesiandaemon.livejournal.com/745835.html

At the north end of the M11, the A14 westbound merges with the M11 northbound, and then splits into an A14-eastbound slip-road and A14 westbound. As far as I can tell, all of the A14 traffic wants to continue on the A14 (there were slip-roads for the M11 sound and A428 east before this), and the M11 traffic normally wants to turn off onto the A14 east. The M11 traffic might want to continue on the A14 west, but it never does seem to. That's hard to describe in words, but it's simple in a picture:

http://maps.google.co.uk/?ie=UTF8&ll=52.232662,0.071239&spn=0.011223,0.027595&z=15

The point is, it represents an interesting rare example of harmony: normally when traffic tries to merge there's a conflict of interest between people who are already in a lane and want to keep their place and people who want to move into that lane. However, here, almost everyone in the left lane wants to be in the right lane and vice versa, so everyone has an incentive to let the others match speed and move across (else they'd be blocking the way for you to move). And this normally actually happens!

Entries tagged with driving

Preventing traffic jams by driving at constant speed

Flash hazard lights to say "thank you"

Parking restrictions

Parking Violation

A14/A428/M11 junction

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