18 votes
Accepted

Why are flyovers/metro rail tracks much higher than traffic?

If I'm understanding your question correctly, you're asking why a flyover has excess clearance beneath it for traffic below. For example, if the tallest vehicle expected beneath the flyover is 12ft ...
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  • 3,587
14 votes
Accepted

How do train tracks handle really cold weather?

Precipitation Snow Snow can be a problem for running trains, but it really doesn't affect the rail/ballast. Just like on highways, the snow needs to be moved away, but it doesn't have many other ...
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  • 10.7k
14 votes
Accepted

How many train passes can railway tracks endure?

This is an admittedly North American response. MGT In the US, how much traffic goes over a given track in a year is measured in Million Gross Tons (MGT) e.g. 1 MGT = 2 000 000 000 lbs [spaces ...
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  • 10.7k
13 votes
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Why does public transport uses compressed air to open doors instead of electromotors?

Do you mean, for example, a bus entry door? It may be as simple as the "service factor" for motors ("electromagnetic devices") as compared to pneumatics. Inexpensive motors with sintered bronze ...
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  • 353
9 votes
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For train track, why does the ballast need "good drainage"?

There are a number of good reasons why the ballast layer needs to be free draining. The main objective of the ballast layer being free draining is somewhat tautologically to keep the water out of the ...
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  • 206
7 votes
Accepted

How to notate the position of a train?

Speaking personally (as someone who deals with this sort of thing for a US Class I on a regular basis) -- operational and maintenance personnel find railroad locations the same way you and I find ...
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7 votes
Accepted

How are maximum speed limits determined for banked curves?

This information comes from a design document by the Iowa DOT (US). It might not apply everywhere in the world, but the considerations are probably universal. For clarity, the amount of banking of a ...
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  • 10.7k
7 votes

Why does public transport uses compressed air to open doors instead of electromotors?

They are smoother and if something gets caught in between them then the maximum force it can exert is capped depending on the pressure and the piston area. This means that a trapped limb is less ...
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7 votes
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Is there any reason why "inner-flange" style trains are almost universal?

If you leave off the flanges and just use cones that are solidly connected to an axle, then cones that taper outward (get smaller as they go out) tend to be self-centering but undamped (or underdamped,...
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  • 2,228
6 votes
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How does the pressurized suspension of the Hyperloop not affect the tube pressure?

The air used for the air cushions will come from the air still in the tube pressurized by the pod itself. Thus the system remains closed (all air that is released is sucked out of the environment).
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6 votes

Are rocket engines practical for commercial aircraft?

At a fundamental level, it should be clear that throwing stuff out the back is going to be less economical than sucking in stuff in the front and throwing it out the back faster. For one thing, the ...
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  • 11.3k
6 votes

Why did Jersey barrier bridge rails become the dominant type of highway bridge rail?

I've done some research on New Jersey barriers a few years ago and came across this article by the FHWA. The basic operating principal of the barrier is to dissipate some energy and redirect and ...
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  • 628
6 votes

Why don't public transport networks have more routes to each terminal?

The main reason is economics. Who is going to pay for all the additional lines? The other part to this is, will the additional lines have enough passengers to make them profitable and sustainable? If ...
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  • 9,527
6 votes

Why don't public transport networks have more routes to each terminal?

Keep drawing combinations. You forgot Østerås to Vestli, Østerås to Bergkrystallen, and every other combination of possible origin and destination. This breaks down in a hurry. By the time you ...
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5 votes

Vehicle load factor discrepancies

I think you are possibly concentrating on the wrong thing. From your state.pa.us link: The VLF of a passenger car (.0004) is so small that cumulative pavement impact is essentially moot So, ...
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  • 3,135
5 votes

Which component of vehicle tailpipe emissions has the greatest social cost?

The easy question Do any of the components above have higher costs to society than CO2 per same unit of measure (e.g. gram, kilogram, or ton)? Yes, absolutely. This should come as no surprise given ...
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  • 3,211
5 votes

Monorails - why even have them?

One of the factors is reduction of amount of infrastructure per kilometer (= cost). Monorail is usually elevated on pylons, which means little disruption to the land below (which, in case of normal ...
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  • 6,133
5 votes
Accepted

Why do trains use the same wheels for staying on track and propulsion?

Trains do sometimes use different means for propulsion: Rack railways use cogs, and Funiculars use ropes I think the reason these are uncommon is that the available traction of smooth tracks is more ...
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  • 136
5 votes

Speed breaker design

Shallow, wide speed bumps are easy fore slow traffic while offering more or less the same impact as narrow, high speed bumps. Because the impulse force remains the same for fast speed. They are having ...
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  • 21k
5 votes

Which is fuel efficient, roadways transport vs waterways transport?

Unfortunately, this question shares multiple similarties to the phrase "How long is a fish?"; meaning that the answer is very dependent on the assumptions, limitations and scope of your ...
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  • 314
4 votes

What is required to implement Positive Train Control on railroads in the US?

Speaking personally (I work for a US Class I as a software developer, working with a system that will interface closely with the PTC implementation at my company and knowing developers who have worked ...
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4 votes

Why are flyovers/metro rail tracks much higher than traffic?

In the United States the public safety standards, designed by the American Association of State Highway and Transportation Officers (AASHTO), require that: Vertical clearance on State trunk ...
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4 votes

Are rocket engines practical for commercial aircraft?

Economically a rocket engine will always lose out to a jet engine. We'll ignore solid fuel rockets, they are impractical for commercial air travel due to their fixed thrust and inability to turn on ...
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  • 766
4 votes

For train track, why does the ballast need "good drainage"?

For both kinds of track, the answer is the same: to prevent the track from shifting as a result of freeze-thaw cycles. The idea with ballasted track is that water is not allowed to accumulate in the ...
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  • 6,759
4 votes

Why do trains not have a high-friction emergency braking system?

Another contribution to the issue, if you want to stop a train of any length in a hurry you would need to uniformly brake every car in a controlled way. If you excessively brake the forward part you ...
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  • 979
4 votes

Is there any reason why "inner-flange" style trains are almost universal?

On a fast curve the outer flange ( on the inside of the curve) will lift off the rail and the train will leave the tracks. While an inner flange is pushed down onto the rail giving more stability.
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  • 5,894
4 votes

What are these reflective triangles on the sides of train track rails for?

They are markers used for accurate position monitoring, without the need to close the tracks to trains and allow people to work close to them. All the markers can be scanned from a few fixed points (e....
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  • 12.5k
4 votes
Accepted

What do we call these "transport frames made of wood" (обрешетки in Russian)

The English term for this is definitely crate.
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4 votes

On the steam locomotives, why was the driver's cabin not located in the front of the boiler for better visibility?

There have been some locomotives with this design, it's called "Cab forward." As the article says, Southern Pacific railroad in the US had some cab forward locomotives, which solved crew ...
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3 votes
Accepted

Why use rectifier / inverter in locomotives?

To change varying AC to fixed AC .for example the alternator that is attached to the engine will output varying AC voltage, whose frequency would be different from the operating frequency or rated ...
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