Stopping distances experiment #2: The real world

Last week we discussed a (flawed) stopping distance experiment, where we argued that you cannot stop from 18 mph to 0 in 6.5 metres, no matter what the police claim. That's when you are prepared to halt and planning the exact moment to pull on the levers.

What does it a real emergency halt look like? It looks like this video. Taken about half an hour before the one of a BMW driving down a pavement to get past a traffic queue, for reference.

Here is what it looks like when someone runs out in front of you while you are freewheeling down a hill (Hampton Road, BS6). Speed? Let's assume 18-20 mph. You can hear from the noise of the (hope) hubs that there's no pedalling, so this is just a gentle 5-10 mph curve round the mini-roundabout-of-death, a few spins of a drivetrain in precisely the low gear you are always in when you come up the hill from the Arches, and then coasting, relying on gravity to do the work.

• 0:26 small kid runs out from some cars, looks like 3 parked car spaces away. Assume: 12-16 metres.
• No previous visibility, on account of the cars being bigger than him.
• 0:27 cyclist sees this and shouts "wooah!"
• 0:28 bike catches up with where kid was: he's run on to be with his friends. (Assuming 16 metres, that puts velocity at 29 km/h)
• 0:29 cyclist has now slowed down to the kids running-along-the road pace. Asks child to look. Child doesn't appear to hear them.

The entire incident is over within five seconds. There wasn't enough time to slow down before any collison would have occurred. Shouting and swerving while you slow down is all you have.

The gradient of the hill will have made stopping hard, and this wasn't the "prepared for emergency brake" setup of our previous experiment. This is real world going round the town with your hands on the tops of the levers, with gravity fighting the decelleration. The combination of the time to see and actually slow down puts the total stopping distance at something like 20 metres.

Brakingdistances.com says you for a car @ 30kmh/20mph on a -12% gradient you shoud expect 6m of thinking, 14m of stopping. Which seems consistent.

Now imagine that incident happens once a "Kim Brigg's law" is passed: a pedestrian crosses the road, cyclist > 12m away, travelling at 18-20 mph. Cyclist sees pedestrian, shouts out. Tries to veer to the side, hits the child instead. That would appear to be enough to get the mini roundabout reinstated as Bristol's Public Gallows, and your eviscerated remains left to hang for days as school parents block the roundabout in their Volvo XC90s. "Look at that cyclist, he deserved it. Now, why is this anti-car council stopping me from driving at 30, can't they see I'm late for school?"

Who is to blame here?

It's not the kid's fault he wanted to be with his friends, it's not his fault all the parked cars made him invisible until he ran out.

He didn't look. Maybe he was enthusiastic about wanting to be with his friends. Maybe he listened for a car, but didn't hear any engine, so carried on out. Children are like that: Enthusiasm is not a crime.

What did the cyclist do wrong? Well, that's a question. Is freewheeling down a hill at 18-20 mph speed limit "reckless"? "careless"? Wilful endangerment of themselves and others? The Crown Prosecution would probably argue that, while everyone from the Daily Mail to the BBC would use verbs like "plowed" and "flew" as they covered the trial. In which case: driving round the area at 20 mph, especially in a low-engine-noise vehicle (hybrid, electric) is probably even more wilful.

The one thing you can point to the cyclist and say is: you knew term time had just started, and there were other kids on the pavement. Therefore it was likely there'd be more chidren ahead. So maybe you should have braked all the way down that hill. But: no matter what speed you go down that hill on a bike. if there is a car going the same way, it'll be right behind you or trying to get past.

Which moves to a more controversial question: is 20 mph too high a speed during school start/finish times? Should we drop from 20 mph to 15 in areas near schools? For everyone, drivers and cyclists alike?

Hints of a left hook

Nothing spells "left hook" like a van coming up alongside with its indicators on. However, this one did actually wait for the cyclist to get past.



For London viewers: note the stressful conditions of Bristol streets. This is actually Sustrans NC4, as marked by some fading paint.

For ABD members from Weston Super Mare and 1973: note the parking spaces stolen by the RPZ, the cyclists in one direction, and how a van was held from turning by another bicycle —costing the company and city money.

Roundabout work #2: 08:17

Once the mercedes that blocked vehicles getting off the roundabout had cleared it, vehicles wanting to get onto St Michael's Hill could pull out, and here see the correct tactic: stop cars getting onto the roundabout. It's the only way to reduce demand, and so ensure the junction clears.

Which vehicle do we see here? Yes, its YA55VDY, the cult van of Bristol Traffic

Notice how the vehicle following this car is also in the mini-roundabout, but it hangs back to actually allow pedestrians to cross at the traffic island. Of course, this will prevent vehicles turning right to pull out, which is a bit selfish, but it does allow the roundabout to clear by reducing vehicle ingress rates to match that of egress rates.

The key point here is that it shows that those fellow-motorist-activist groups who advocate removing traffic lights are either missing the point or hiding the truth. On a junction without lights -like this one- the only way to get through is to be aggressive: drive the big vehicles, the 4x4, or even better, the battered big-vehicle, such as the white van. Now we, as white-van drivers, are happy with this, but we think the harsh truth should be discussed in the open, not discovered once they remove lights from the city centre: whoever values their vehicle least wins.

Roundabout work #1: 08:15

08:15 to 08:16 on the top of St Michael's Hill.

First a car with a Montpelier-MOT wingmirror duct-taped into place. Someone just horned it as to get to this part of the junction (see on the dashed lines) it had to sprint up the oncoming traffic lane.

But by doing so it gets to pull out where the mercedes stuck in the middle of the mini roundabout has left a gap, follow the van through to the right and hope that there isn't anyone crossing the zebra crossing, which would block up the roundabout some more.

It does clear, the gap allows a car coming up Cotham Hill to pull out and turn right into St Michael's Hill.

Or it would, if the Mercedes hadn't stayed where it was.

Do you see what's wrong here? By staying back on the mini roundabout, by allowing cars out of Cotham Road, the school-run-driver is, sadly, making things worse. All the vehicles who are held up on Cotham Hill will see this and drive more considerately.

Double Jeopardy

We think this is wrong.

The poor owner of LG55URR is only parked across a dropped kerb near a school, so why on earth has he or she been given TWO tickets?

We suspect this is probably just west-country persecution of Londoners in Bristol, which is not surprising - after all they're still getting Crossrail, whilst Bristol can't even get a decent bendy bus.

Maybe they just get so chilled and mellow when they arrive here that they forget to drive.

Dropped Kerb Parking Persecution

Since March 1, the council has been promising it will make life harder for us, the city's tax payers, by ticketing our cars on dropped kerbs. And its true, they really are!

Here by Hampton Road and Cotham Vale, HD53UHB has received two tickets.

It's crime? Being parked across the knobbly bit of the pavement -that's all.
 

That's despite the fact there is clearly enough room for a student to walk up the hill and out onto the road -while talking on their phone- we note. Why don't mobile phones detect when someone is using them at walking pace and stop working? Because the telcos make so much money from students strolling around, chatting to their mates, that they don't want any ban on walking+mobile phones.

Over in Beaufort Road, Clifton. Another corner. another car, A3FXX, ticketed.

A week later we can see how the locals have learned and adapted. WP52EFH shows the trick.

If you park far enough away from the dropped kerb, you are no longer blocking pedestrian access. That's OK then.

School trouble

Today is the 10th anniversary of the Columbine massacre, an event that not only brought tragedy to many, but is why whenever police and ambulance get called out to a school, everyone worries, especially the parents.

For an as yet unknown reason the paramedics came screaming up to the top entrance to the St Peter's and Paul's primary school in Cotham at:16:50 this afternoon, -and hour later there was a row of police cars.

Access has been fenced off, the police were removing a few paper bags of stuff

Meanwhile, up on the roundabout, the local commuters where helping to calm traffic by blocking the junction.

There's no news yet on why the ambulance/police were round, hopefully it's something minor.

Hiver sur l'Alpe de Saint Michel

This is the top of St Michael's Hill at 09:18. There is no traffic, as the only way to get here is uphill, and uphill isn't working.

On Hampton Road, someone has abandoned their car where it chose to slide.

Looking towards the Highbury Vaults pub, there is no traffic at all. It is silent. Usually of a morning there is a jam of cars heading in from the M32-way towards somewhere, and cars waiting to turn right into Tyndall's Park Avenue, and hence Clifton, cars often full of schoolkids. Not today. Today, nobody but a pedestrian. Today, the pedestrians are in charge.

The cars on Hampton Hill are parked; they decided (wisely) not risk the downhill. They must have successfully made it up, then realised the price of success is the descent. Which is often the most dangerous part of mountaineering, as it harder to control your speed. Which is why mountaineering normally views a "successful" summit attempt as one where at least one member of the party makes it back. Any expedition where you top out but don't reach the mountain hut for beers afterwards counts as a failure.


That doesn't mean that the summiting process is is easy; here's someone showing how much effort it takes to get a rear wheel drive to get up to this roundabout. And, since they are not one of the parked cars, they must have made it to wherever they were in a hurry to get to this morning.

It's the only vehicle breaking the silence.