A question about vehicle safety
April 27, 2013 9:27 AM   Subscribe

Why don't trams/streetcars have a front bumper that almost touches the street, and slants out like a plow, so that if they hit a pedestrian they'd knock them aside rather than running them over? In fact, why don't trains have this, or even cars?

I guess what I'm picturing is a bit like the plow-like skirt at the front of an old locomotive (is this why they had those?) but it wouldn't have to be that large or prominent. Just enough to keep anyone from going under the wheels if they were hit head-on.

The only issue I can think of is that it would scrape the ground going uphill, but surely that's a solvable problem, right? You could use stiff rubber with little wheels at the edges, or some other flexible construction.

I realize that some high-speed collisions might still be deadly just from the blunt force trauma, but with something like a tram that never goes that fast, it would often mean the difference between life and death. How many people are hit by trams each year? Wouldn't this be a relatively cheap and easy way to save lives?

I feel like I'm missing something obvious here, but what?
posted by pete_22 to Grab Bag (12 answers total) 3 users marked this as a favorite
 
The term for this is "cow-catcher" aka cowcatcher or "pilot"

Lots of discussion of the benefits or lack of benefits for transit cars if you search for "cowcatcher and transit" on google.
posted by bottlebrushtree at 9:38 AM on April 27, 2013 [2 favorites]


How many people are killed by trains each year? It can't be that many. I'm not sure this is a problem in desperate need of solving.
posted by tylerkaraszewski at 10:05 AM on April 27, 2013


Well, I don't know anything about, like, physics or science (haha) but one thought is that the little skirt might cause the car to flip and kill the people inside, instead of just the people on the sidewalk.

And would having that hanging out in front create more accidents? I've seen enough people cut off other people and tailgate other people to think plenty of drivers will misjudge the clearance between the skirt and the cars around them. I assume it would be a uniform size and people would get used to it, but people would still misjudge how far it goes out.

Also, I imagine it would create more congestion on roads. Cars would be longer and less cars would fit on the road.
posted by AppleTurnover at 10:06 AM on April 27, 2013 [1 favorite]


Trams and streetcars benefit from having a round nose when making their urban turns, while having a giant v-shaped cowcatcher would sweep out an arc at every turn which extend away from the track and would be a serious hazard to peds. I suppose an independently-angled unit under the nose but which was steered by the shape of the track, rather than the position of the nose (remember that the front wheels are generally behind the nose by several feet) would fix this, but that's more moving parts and more parts engaged on the track.

Stats from the 1990s show that total fatalities from urban transportation, which includes collisions, derailments and so on, not just peds being hit by any mode, were around 300 people/year, give or take. By comparison, auto fatalities in the same years were around 17,000 (nearly 33,000 in 2010, see next link). NHTSA stats here (for the 2000s) show that peds make up around 13% of the fatalities, so while public transit is killing riders and passengers to the tune of 300/year, cars are killing between 7 and 14 times as many pedestrians alone. Further, 60% of the peds were at least partially intoxicated with BAC >0.80%, which is too drunk to drive in most states. (Freakonomics notes that the statistics indicate it's therefore safer to drive-- I say it's safer to be inside a car when another car hits you thanks to your own fool drunkeness.)

IMO, money would be better spent creating better warning indicators, and doing what it takes to encourage the drunk to actually ride the transit system, rather than getting in its way.
posted by Sunburnt at 10:26 AM on April 27, 2013 [2 favorites]


Cars don't have this (and other safety features) because it would add too much weight or cost. If it adds weight, the car won't meet CAFE fuel economy standards and then can't be sold in many countries. If it adds cost (e.g. if lightweight, expensive materials are used to keep the weight low), the car will cost too much and no one will buy it.
posted by sninctown at 10:28 AM on April 27, 2013


the 'cow catcher' isn't designed for the safety or well-being of cows (or pedestrians)...not in the slightest. It's not even a concern. It doesn't work that way.
The point of the 'cow catcher' is that when you hit a cow wandering the tracks at 50+mph it doesn't cause the entire train to derail, killing everyone on board. Sure, at slow speeds, it nudges them gently off the track, but at high speed? Yeah, they die. The reason you don't see them so much anymore is that farmers finally got the message and started keeping their cows penned up.
posted by sexyrobot at 10:56 AM on April 27, 2013 [6 favorites]


I was working on a script recently for a Mercedes-Benz training program and one of the "core feature" points it included was the lower front bumper height of their models, engineered exactly for this reason (to hit most pedestrians below knee level and sweep them over the hood, instead of pulling them under the vehicle). So maybe having something extend all the way to the ground isn't necessary to get the same benefit? Just speculating here.
posted by Revie1 at 11:25 AM on April 27, 2013 [4 favorites]


Pedestrians aren't really the issue with trams; trams are more likely to encounter cars.
posted by KokuRyu at 11:29 AM on April 27, 2013 [1 favorite]


I try to explain a couple of things that answer your question (or at least contribute to the answer to your question)...

1. Anti-climbers / Anti-Climbing Requirements
There are crew safety requirements for rail vehicle design which mandate that in case of collision (specifically between two rail vehicles!) the design shall prevent one vehicle lifting up and crashing into the crew compartment. A 'cowcatcher' on the front of the tram could provide a ramp onto which a crashing vehicle would lift up and drive into another other vehicle.

2. Loading Gauge
I want to add something to what Sunburnt wrote:

Trams and streetcars benefit from having a round nose when making their urban turns, while having a giant v-shaped cowcatcher would sweep out an arc at every turn which extend away from the track and would be a serious hazard to peds.


This additional 'arc' which Sunburnt described being swept out on each turn would not only pose an additional risk to pedestrians, it could also violate the 'loading gauge' - the cross section within which the train/tram is allowed to run. The wikipedia article describes it better, but the loading gauge describes the 2d cross section in which the tram/train is allowed occupy and within which no track based infrastructure are allowed. Vehicle design must take into account the worst case condition when defining how large the carbody can be. This considers length, position of the trucks, worst case compression of suspension, maximum throw of the front and rear in curves etc...

As Sunburnt wrote, a large cowcatcher in front could violate the loading gauge and hit/scrape curbs and station platforms in curves (for example).

In spite of both of these there are still obstacle deflection devices on the front of trains. They have to fulfill the two requirements listed above:

Look at this cowcatcher / snowplow on the Swiss Re 485 operated by BLS.

The Cobra Tram in Z├╝rich was in the news a couple of years ago being criticized exactly for this.

The Swedish heavy haul IORE locomotive has an extremely large snow plow designed both for snow and reindeer collisions.

But, the main reason this isn't done is that national rail authorities (like the EBA in Germany or the BAV in switzerland or the Federal Rail Authority in the USA have not included this in their acceptance requirements. As long as this isn't mandated by regulatory bodies or required in supply contracts I don't believe any rail builder is going to spend money and time to design design and build something like this.
posted by jazh at 11:40 AM on April 27, 2013 [2 favorites]


So called "side guards" or "underrun guards" are a similar concept for semi-truck trailers. Info: 1, 2, 3.
posted by flug at 1:47 PM on April 27, 2013


I remember reading somewhere that federal regulations changed in the last X years about the design of car front ends. It turned out that the pointy front ends were more harmful to pedestrians because they made a smaller point of impact and caused people to flip over and smash their heads more often. Whereas the newer, blunter front ends were less likely to cause damage.

In other words, if a train/tram/bus is going fast enough that it isn't going to just shove you out of the way, any kind of cow catcher device is more likely to act like a knife when hitting someone.
posted by gjc at 3:20 PM on April 27, 2013


The cowcatcher pictured above in jazh's link for the Swiss train does look like it would do a good job of rolling a human either along the track or out of the way. This is by no means preventing a fatal crushing even at low speed, but it would do significant work towards preventing a person from getting under the train, which would mean all kinds of crazy injuries, up to and including some kind of brutal sectioning by the wheels which would make it super-difficult to keep someone alive, even in a location close to emergency medical intervention. I would say that's not the intention, but as long as it's there, it's entirely possible the human outcomes are improved.

I would also add that most features added to cars for pedestrian safety A) rely on the driver to work, e.g. turn signals, which nobody in my city users, and B) informing the driver by enhancing visibility to blind spots, the cameras covering rear below the truck, headlights of course, window placement, etc. But the safety of the driver is paramount, and it's taken for granted that pedestrians and drivers need to be watching out for one another.
posted by Sunburnt at 7:44 PM on April 27, 2013


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