Safe Speed Forums

Die hard petrolhead though I am I have to agree that trams have their place. It's easier for me to get to Croydon since the trams were introduced. Instead of fighting traffic all the way to Croydon, I fight it as far as Wimbledon and get the tram the rest of the way. I had no idea they stopped so quick though - point in the tram's favour there. One point against is that on roads where trams and cars share the rails can adversely affect the braking abilities of cars. I've been a passenger in a car where the driver was on the rails and had to brake, and it was moderately hairy. That was in Melbourne during a very dry summer, so I'd hate to have to hit the anchors on wet rails during a British winter . BTW, Ocker driver so he would have been used to it, but that didn't make the rubber grip the steel any better. The only other thing that annoys me about trams is this eco-friendly positive spin they get, which is crap when the electricity they run on is made by burning fossil fuels. I just wish they'd be honest and admit that they've just moved the problem. Other than that, trams are pretty handy.

_________________
Make everything as simple as possible, but not simpler - Einstein

What? Inability stop a safety advantage? Are you being sarcastic?

Perhaps my car-into-solid-wall comparison was a touch misleading, but the initial implication that trams are so much more unsafe than cars got me a touch riled... I really should count to 10 before replying The Croydon trams manage 0.3g (http://www.kiepe-elektrik.com/english/schienenfahrzeuge/croydon/), with other modern designs having similar figures. Just comparing cold hard figures, the car wins every time.

However, how many drivers are in cars which can achieve 0.9g braking in the first place, and how many of those drivers then use the full braking force available to them (assuming they're not driving a car fitted with an emergency brake assist system) when making an emergency stop? All the driver of the tram has to do is hit the emergency brake switch (triggering the tram equivalent of brake assist), then hold on tight.

So I guess it's fairer to say that, in optimum conditions, a car will easily out-brake a tram, but in typical conditions the difference is barely worth mentioning, and it's quite possible that the tram would actually stop sooner. It certainly doesn't seem fair to use braking ability as a way to criticise trams.

No, these are general rules of all systems. Deterministic behaviour (routes, stops, trajectories) are the safety advantage. They allow absolute safety measures to be implemented, i.e. safety measures can be built around known behaviours. In a system that uses deterministic routes and stops, it is possible to guarentee (within certain constraints) that no safety risk exists. This is not possible in non-deterministic systems - in such systems, risks must exist, rather than may exist.

_________________
I stole this .sig

So what are we saying about tram safety?

Basingwerk,

The ability to steer around an obstruction is a big advantage not to be sniffed at. Cars can. Trams can't.

The braking thing.

At 0.3g deceleration from 30mph the tram will stop in 133 feet. If we limited trams to 25mph, it would take 97 feet.

At 0.9g deceleration the car will stop from 30mph in 66 feet.

If we assume that braking distance is indicative of the safety of a speed, and that a tram braking in 133 or 97 feet is "OK" for safety, then we could allow cars to travel at:

133 ft = overall car stopping distance from 47mph.
97 feet = overall car stopping distance from 39mph.

Since cars also have a chance of steering around "Little Johnny", I think we could set the limits even higher if we accept that trams are "safe enough".

Actually, in truth, I don't believe that tram stopping distances are much of a problem, neither do I believe that precise use of the speed limit is of any help to road safety. The bottom line is that braking distances are totally unimportant while the usual safety systems are operating OK.

But IF speed limits are important because of braking distances THEN trams are dangerous.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Or perhaps even more usefully:

If trams are safe enough then braking distances are not very important.

AND

If braking distances are not very important then neither is precise adherence to speed limits.

THEREFORE:

IF trams are safe enough THEN precise adherence to speed limits is unimportant to road safety.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

But the ability to stay on track and never veer off line into another tram is also a big advantage. Trams can. Cars can't.



With all these cars veering off line into you, it is a good job the brakes are good. Trams, on the other hand, should occupy thier own road space, with access to the tracks strictly limited. For example, the trams along Landesberger Strasse in Munich between Hauptbahnhof and the Mittlerring, have perhaps two or three sections over a 3 km run where trams could interact without interlock lights. That is one of the places that I got caught out on, but I only did that once. The trams along Ganghofer Strasse, on the other hand, used to run along the road between Harras and West End Park. It gets a bit dodgy there, especially near the top of LindenStrasse. But don't forget, the public transport system in Munich has made cars unnecessary. They have a U-Bahn system like London but clean, effective and cheap, with trains every 5 minutes from 5 am up to 1 am. Terminals are conected by trams and busses. On top of that, they have a standard rail system, and then also the S-Bahn, which reaches all the outlying villages to a dustance or 20 or 30 km.

You really should go there and check out a fully integrated public transport system - no one in this country can even start to understand one without visting Munich. Transport in the UK is a noddy system totally dependant on cars. Montreal is not far behind Munich. Check out the Montreal underground, again cheap, fast and clean. Also, it is well integrated with the bus system, and the city airport (Dorval) is 15 minutes from downtown. Really great, again in the UK we can't imagine a good system because ours are so bad with nothing but congested roads everywhere, and fed up motorists in jams.

_________________
I stole this .sig