The 'Car Train' - would it work?

Great Debates
21

Sam, I’m starting to get the feeling you opened this thread to bash trains. Which is just bizarre. It is an unusual conclusion to come to, but you’re acting unusual. Your numbers are very much what you want them to be, and not very much reality.

Most people don’t drive around with an extra six-tenths of a person with them. By far the most cars I see on the road are occupied by a single person. The extra .6 in the average probably comes from large families on road trips, etc. You know, the exceptions, not the rules. And most hybrids don’t get 50mpg. The two most popular - the Prius and the Civic, get in the 40s. You also ignored what I said about our country currently being more geared toward automobile transportation.

The bizarre thing is that you’re by far smart enough to know all this. You must have deliberately omitted it from your arguments. Why?

22

Toyota unveiled a concept car in 2003 - the Personal Mobility concept car, one feature would be
*
“to share the burden of driving, multiple PMs can team up in a lead-follow arrangement. One PM can become the lead vehicle, while others follow on autopilot. The following-position vehicle’s on-board computer controls handling, throttle and braking, and maintains a safe distance from other PMs in front or behind. However, the following-position PM surrenders direction and steering to the lead PM. The lead PM driver is in charge of direction and speed. This autopilot feature is convenient for guiding a group of PMs (e.g., car pooling), or if someone is more familiar with a particular area and might know a shortcut.”*

The concept was scaled down to truer personal mobility device, i.e, a very smart, and well-powered motorized wheel chair. The latest generation seems geared more for pedestrian pathways, rather than being a street vehicle - which could probably find a market in Asia and possible Europe, but not in the Americas (with the exception of Southern Florida and other retirement communities).

But at least one major automaker has considered the concept, though I dont think they were intended to have physical linkages, but just network connections. But I dont think the barriers to entry are lack of automotive technology, but confusion in regards to legal/liability issues, and ensuring security so that the vehicle would not get hacked. And I think being a ‘lead driver’ might require a specialized license such as motorcyclists and commercial drivers have. (Actually, I would bet serious money the insurance companies would mandate it!)

I am seriously looking forward to the headline though:

“Car Hacked in Los Angeles!
Driver found unharmed after she was safely ejected into a nearby park. According the vehicle’s GPS lowjack system, it is currently in Thailand, but authorities believe that system may have been overridden as well.”

Car thieves of the next century wont need metal keys or even keycards, but a set of cipher keys. Overdrive may have a whole new meaning also.

23

I actually did not do that. I opened this thread to discuss an idea that I thought was interesting. I did not find out the fact about the energy cost of trains until I started trying to put some numbers to the various efficiencies of the ‘car train’. I posted about it because the numbers surprised me. In fact, they rather took the wind out of my grand plan.

I honestly expected passenger-mile train efficiency to be an order of magnitude better than a car.

You mean, like most inter-city trips? Which is what we’re talking about?

And some passenger trains run mostly empty, and some run full. Which is why it only makes sense to talk in terms of averages. Look, I know there are variables here - Perhaps if you got rid of the car, trains would be more full and the passenger-mile energy cost would go down. But I don’t know that. I do know that the numbers we’ve got, based on averages, are very close. So much so that if you want to make the inter-city transportation system more efficient you could do more by just encouraging car pooling and smaller, more efficient cars than by packing people into trains. Or so it seems to me. Tell me where I’m wrong.

But I’m not talking about current cars. I was talking about a newer, more efficient transportation infrastructure. I started this thread by assuming that trains were much more efficient, and that something like a ‘car train’ might bring the efficiency of car travel into line with the train. After looking at the numbers, it seems that much smaller improvements could do the same thing.

Please. Accusations of lying and disinformation are hardly warranted here. To me, it looks like I found some surprising information that casts doubt on the train as being significantly more efficient than the car - enough so to warrant spending huge sums to build new train infrastructures - and you see this information as threatening to your own biases and becoming correspondingly defensive about it.

I have no reason to assume that the Department of Energy’s numbers are wrong. Therefore, it seems to me that passenger-mile efficiency of the train vs the car is close enough that reasonable improvements in fuel efficiency or increases in the average number of people in a car could tip the scale in favor of the car.

24

I agree, and based on averages, the train is A LOT more effecient, but you keep bending the averages your way.

You’re washing out a 25% advantage. Like I said before, I think 1 or 2% would be huge on this scale. Someone please correct me if I’m wrong about that.

But the information says the exact opposite of that. It says the train IS significantly more efficient than the car. If you assume that with effort the car could become more effecient, then you have to assume that with effort the train could become more effecient.

No. I am not train-biased. You and I looked at the same thing and saw something quite different. I’m only defending what I saw.

25

Among other things as mentioned in the OP, trains main source of fuel economy comes from the fact that it doesn’t have to start and stop. The steel wheels help quite a bit, too. But as has already been mentioned, a car’s engine is designed for that car, not to haul 10 other cars around. The only advantage you’re going to get is with a system like the one Agnostic Pagan posted about Toyota. It’ll save you a bit of fuel economy due to air drag, but that’s all we’re going to save, in reality.

26

You’re off by hundreds of miles - the train runs from Lorton, VA to Sanford, FL. Lorton is just south of Washington, DC.

I have gone to that station to meet family members riding up from Florida - their ultimate destination was New York, and they had a huge drive ahead of them.

27

I think Dan has an interesting extension of Samstone’s idea here. There could be like a carpool lane except its a conga line of networked (and possibly linked) cars that you can join if you’re gonna be cruising for a while.

28

Why would I lash my car to a dozen other cars instead of taking an ACTUAL train?

Google “automated highway system”. It sounds very similar to your idea, except better because it’s automated. You don’t have to get together with a bunch of strangers and tie your cars together.

Basically the idea is as you get into special highway lanes, sensors will “platoon” groups of cars together so they can safely travel bumper to bumper at highway speeds. It’s really more to relieve congestion although I imagine that there would be some fuel economy benefit from drafting.

The main reason a car/truck is inefficient compared to a train is that it’s payload is relatively small compared to the rest of the vehicle. 100 engines pulling a 100 small loads is a lot less efficient than a single engine maximized to pull one equivalent big load.

29

Santo Rugger I think that you way underestimate the importance of drag at highway speeds. Those of who cycle know it very well which why cyclists often travel drafting off of each other in pacelines. The longer the line the better and even the lead rider benefits some from the effect as he avoids the drag of turbulence behind him. Cyclists drafting just as a pair at 20 mph reduce their energy consumption (as measured by VO2max) by 18% and at 25 mph they save 29%. A group of 8 cuts down energy consumption by 39%. (Source) The group functions to the air as one object, one long narrow, low Cd object. The effect on cars is much more significant as, obviously, the effect becomes much larger at higher speeds. To give a sense of the savings a cyclist behind a truck saves 62% of their energy. Auto racers know this and utilize the “slipstream” effect to slingshot out in races. (Shake and Bake!) Seriously.

A limiting factor is that cars cannot get too close (even under computer guidance) because so much air flow would be cut down that the nonlead cars would not get enough air flow to function efficiently.

The idea has been seriously studied.

30

Because when you get to your destination, you still have your car.

Because it’s your car, it can be outfitted to personalize your needs. Rather than sit in public with a bunch of other people, I can remain in the privacy of my own vehicle. It’s like a private train berth for every group.

Because you don’t have to build tracks everywhere.

Because if the changing economy causes the flow of traffic to change, you’re not stuck with a fixed train infrastructure that no longer services your needs.

Because you can make these things of arbitrary sizes and use existing roads, they can always go places trains will never go, like between a factory and a bedroom community, or for workers transiting from one job site to another (shift changes, etc).

Because you don’t have to wait in lines for tickets, cabs, or go through security.

Because you’re safe from the public. The last two times I took my daughter on light-rail transit, it was very uncomfortable with threatening teens being in the same car, a couple of kids swearing at each other like mad, etc.

I’d ask you the reverse question: if I can get the benefits of a train just by electronically lashing some autos together, why on earth would I ever want to ride a train?

31

Build self-driving cars that know where they’re going and coordinate with each other.

If every car in ten miles knew what the other cars were up to, and humans were not driving ANY of them, there’d never be a need to stop at a traffic signal at all unless pedestrians started crossing.

Such cars could readily draft, as in this ‘car train’ idea, but also adapt. The cars would know exactly what ‘train’ to join, and cars that left the train would simply cause the remainder of the train to link up and carry on.

Most important, self-driving cars would be patient and law-abiding, something virtually no human driver is. They’d take their time, and get there when they get there, while the occupants daydream, read, watch TV, get drunk out of their minds or whatever.

Naturally, tampering with this ‘patient’ AI should be a criminal offense. Cause a wreck, and it’s 100% your fault, whatever the cost or consequences. By then every car would have cameras (just to ‘see’, if for no other reason) and would be patiently uplinking high resolution photos and GPS coordinates into the police computer with ‘complaints’ about anti-social vehicles driving erratically, so enforcement becomes a no-brainer. No cellular connection? No problem, they just remember the incidents until there is a cellular connection. Sixty computerized witnesses to the crime.

Without this ‘AI Complete’ component, the ‘car train’ could never safely operate. PEOPLE would screw it up, and the system its self couldn’t react to unforeseen irregularities on a road, like a sheep wandering onto the highway.

32

I think the OP is sweeping too many things under the carpet with this idea. I think safety kills the concept dead in the water before any of the other arguments.

If the cars are not physically connected, the reliance is on each one’s ability to maintain separation by powering and braking in unison under all circumstances. The front car mustn’t decelerate faster than any of the following ones, for any reason. Even with computer control, I don’t think that could be guaranteed. At tight spacings it would only require a small difference in actual braking effort, close the gap, and create a chain reaction. These are vehicles that are privately owned, of different ages, makes and loadings, with different servicing histories, different tyres etc. Even if your computers can figure all that out on the fly, and stay connected together, the road surface itself could have many subtle variations in gradient, pavement, ice or water cover. Add in too the potential non braking related sources of deceleration. Front car hits a solid object, a moose, boulder, another car, and is slowed suddenly by the exchange of energy. All the trailing cars are going to be able to cope with that? I don’t think so.

So you might have to couple the cars physically. That lessens the combined braking issues somewhat, now the worst you can have is a multiple jack-knife. But the coupling of each car has to be strong enough to withstand any potential forces experienced in any position in the train. If there is even the potential for the front vehicle to tow the rest, the draw gear of each must be able to withstand the buff and draft forces of the combined trailing vehicles. The coupler becomes a large and heavy piece of the car (or a less large and heavy but much more costly thing if it’s made from more exotic materials) that you have to lug around at all times.

The same applies with shared power. The cables on each car have to be heavy enough to potentially supply power to all the trailing cars, another dead weight to carry at other times.

There would have to be standards to ensure interconnectivity, of the mechanical coupling, of the power sharing system, and of the comms and software for the computers needed to make it work. The savings from the convoy would have to exceed the added expense from buying the extra equipment and then carrying it around when not in use. You’d need a critical minimum number of equipped cars to make it work. People would have to be convinced to buy a suitable car years before there would be enough of them to see any benefit.

I don’t see the wisdom is increased tyre pressures here. Either you want tyres with a lower rolling resistance, all the time, or you don’t. In the convoyed configuration, you need the same or better braking and handling than you would at other times, and in many cases higher tyre pressure would benefit these attributes, over “standard settings”. But why not have that all the time? Ride comfort and uneven wear. So you want to put up with a choppy ride while in convoy? You’re on the same roads as all the other non-trained cars, according to your own scheme. The right tyre pressure is the same in convoy or not.

I’m not keen on the figures comparing transport modes and BTU’s, not for this exercise. Too simplistic. Also the thinking of comparing cars and buses and trains leaves out the most likely competitor, aviation. European model high speed rail systems would more directly compete with planes than with cars. As we’ve seen above, some people just aren’t going to get out of their cars and onto any form of public transport for reasons that have little to do with economics and more to do with culture. For everyone else though, those not paranoid about sitting next to a stranger, it’s plane versus train.

The fickle finger of fate being what it is, I can just picture poor old Sam Stone, safely coupled up in convoy, only to find that the car in front is full of unruly teens. Clunk! Another soda can bounces off the windscreen. “Gee, that young guy in front really needs to learn to wipe his backside properly if he’s going to do that…” Are we there yet?

:eek:

33

How is this going to work with my hovercar?