# Questions tagged [transportation]

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### Theory of rotationally symmetric air cushion vehicle

I am trying to develop a theory for this situation: A small blown-up balloon is attached to the center of a compact disc; you let it float as the balloon discharges. Simplifying assumptions: ...
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### I don't understand how the pneumatic control precession actuation on the Brennan Monorail's gyros further balances the vehicle

I linked a YouTube video from Primal Space, The Self Balancing Monorail, discussing how the Brennan Monorail works. @6:40 timestamp the narrator explains how the pneumatic pressure "[pushes] the ...
1 vote
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### What is the fastest way to move a 720 ton statue for a distance of 500 km from Cairo to Luxor with modern technology?

The ancient egyptians could do it but we don't know how long it took them. What would be the fastest way to do it with modern technology? How long would it take? https://en.wikipedia.org/wiki/...
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### The heaviest road-legal truck

The question is what is the heaviest road-legal truck? I exclude road trains (except for one full trailer in addition to regular load) and special payloads (such as wind turbines, very large ...
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### Why are expansion joints on prestressed concrete box girder bridges sometimes not located directly above the bridge piers?

Here is an example of what I am referring to. This bridge is part of the Tom Moreland Interchange in Atlanta, more commonly known as "Spaghetti Junction". This interchange has several ...
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### speed-density relationship transportation question

I have the following questions: Would the capacity be the area under the curve? Or can I use this formula: $q_c = \frac{k_j \times v_f}{4}$ from the greenshields model, where the capacity flow is ...
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### Why can't the 'special values' in the transportation fundamental diagrams always be determined?

Why can't the 'special values' in the transportation fundamental diagrams always be determined? For example: Why can't I always determine the Free-flow speed (𝑣A), Capacity (𝑞B), Critical density (�...
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### Which is fuel efficient, roadways transport vs waterways transport? [closed]

Which will be more efficient in term of fuel price: Transport via roadways, say truck or motor vehicle. Transport via waterways, say via ship or motor boat. Assumptions: Same caliber engines (same ...
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### Narrow Gauge HSR [closed]

Would it be possible to build a High-Speed Rail on narrow gauge by making it electric (low centre of mass due to battery weight = higher stability) and reducing the friction on the wheels (lubricant?)?...
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### Moving a small aircraft over grass in winter

I really hope i am in the right place for this question. In a flight club we have an aircraft that weighs about 480kg. On the ground it taxis (drives) on three small wheels while only two of them are ...
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### How are ships stacked ontop of other ships?

As shown at this skeptics SE post, there are ships that carry other ships as cargo, etc... My question: how are the ships stacked onto the flat bed ship? Is there some kind of specialized crane that ...
46 views

### How can I integrate a system to track a tractor's movements in a field using GPS? [closed]

I work in agriculture and I'd like to track my tractors "trips". What I'm looking for is a device that will record this data using GPS, and send it to a database to later process it. I ...
1 vote
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### Is there any more convincing exemple of the Braess Paraxod than the diamond-shaped network?

The Braess Paradox is the observation that adding one or more roads to a road network can slow down overall traffic flow through it. This paradox supposedly applies for cars on highways but can extend ...
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1 vote
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### Why are different tractor trailer hitch configurations used in different regions of the US?

This may not be the best SE site for this question but I figured there had to be some engineering insight behind it- I've noticed in the western US tractor trailers have much longer hitches, like ...
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### Why are trams always electrified with DC, while trains can be electrified either with AC or DC?

Trains can be electrified either with DC voltage or with AC voltage. Various networks across various countries uses various standards. My question is however for trams, which are basically a lighter ...
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1 vote
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### On the steam locomotives, why was the driver's cabin not located in the front of the boiler for better visibility?

I always wondered how the drivers of steam locomotives could observe the road.
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### Speed breaker design

Speed breakers are safety devices that keep check on the fast-moving traffic. But what does the speed breaker do when the vehicle is already slow approaching. Is there any better breaking system ...
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### Why culmination points in tunnels?

The shortest connection between two portals would be a tunnel with constant gradient. Why do long tunnels instead rise from both portals to a culmination point, introducing unnecessary steep gradients?...
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### Is the assumption that "the passengers go to their destinations using minimal transfers" valid in an academic paper I'm reading?

I'm reading a paper titled "A Simultaneous Bus Route Design and Frequency Setting Problem for Tin Shui Wai, Hong Kong" (W.Y. Szeto, Yongzhong Wu) which attempts to model an improved bus network in my ...
60 views

### Do high speed trains use ventilation and filtration systems similar to aircraft?

This article discusses the ventilation and filtration in aircraft: Ventilation rates provide a total change of air 20 to 30 times per hour. Most modern aircraft have recirculation systems, which ...
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1 vote
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### Why do trains use the same wheels for staying on track and propulsion?

Trains where originally designed to keep the train on track. At the time trains where pulled by horses and used to transport coal (and such) out of mines. The two functions have very different ...
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### What determines when a road should be widened?

I know this depends on a variety of factors including overall traffic volumes, peak traffic volumes, types of vehicles, and type of road, but how exactly do traffic engineers determine how many lanes ...
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### Why rear wheels of the bus are covered?

There is an airport bus (Germany) which has it's rear wheels covered by the fender. Even front wheels have strange shape of fender around them (tilted toward front). What purpose of that?
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### What do we call these "transport frames made of wood" (обрешетки in Russian)

I'm translating a document in which there is a mention of обрешетки used for preparing goods (medical equipment of large size) for shipment. This term derives from reshetka (решетка) - lattice, and ...
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### Has the kangaroo's jumping ever been copied in human engineering?

The kangaroo has incredible jumping abiltiies. Its Gastrocnemius muscle is a major part of generating its jumping force. Has any engineer based a design, probably a vehicle, upon the kangaroo's ...
406 views

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

Last night while waiting for the train at South Yarra station in Melbourne, I saw these reflective triangles stuck on the sides of the train track rails. They were evenly spaced a few metres apart for ...
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### Is there any reason why "inner-flange" style trains are almost universal?

There's basically two ways train wheels can operate, the flanges could be either "inner" or "outer". Switches can be made in equivalent ways for inner and outer flanges. We could expect that, just ...
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### How do trolleybus switches work?

The switches are so high it's not possible to see how they function on the ground. I really tried to look up information about this on the internet, but there's very little info available, and the ...
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1 vote
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### How do maglev trains turn given that they seem to have more than two bogies per car?

All of the images of maglev trains that I've seen seem to have a continuous drive mechanism along the entire length of each car: I assume this must be articulated some how, or the train wouldn't be ...
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### How do you calculate the chain tension required when compressing bulk material over a conveyor?

Bulk material is conveyed over a slat conveyor, and the material is leveled with overhead rollers while being transported in the conveyor to maintain an even material height. Most of these "levelers" ...
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### Why do (some) high-speed trains have curved (convex) walls?

Comparing the cross-section of modern high-speed trains to old train waggons, which had straight walls and were limited to speeds around 200 km/h, I notice that most of them have curved outer walls. ...
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### Is there a particular reason the Moléson funicular is built as a giant bridge?

So I live in Switzerland and there is lots of funiculars in my country. Most of those were built between 1890 and 1930, and for most of those the line is on the ground most of the time, there is ...
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1 vote
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### What determines the maximum possible slope of rail transportation (without rack)?

(Disclaimer: To make things clear I'm talking about adhesion railways and excluding rack railways as those are an entirely different technology and requires specially equipped vehicles. Also I'm ...
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### Purpose of special railway transport wagons? [closed]

What's the purpose of the special railway transport wagons shown in the photograph?
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### Why don't public transport networks have more routes to each terminal?

When using public transport, we often need to change routes in the middle of the journey. These changes have costs – I can think of the following, but there may be more. If we're reading, working, ...
246 views

### Advantages of a commuter train instead of a vehicle travelling in a straight road

Most large cities these days have some sort of metropolitan commuter train system. What are the reasons for the commuter trains, why couldn't we instead of having train tracks why not clear a large ...
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### Standard bicycle monorail design considerations

I have been thinking of a design for a standard bicycle monorail. I don't have the resources to prototype it right now so I would like to bounce the design off the community. Basically thinking of a ...
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### Why did Jersey barrier bridge rails become the dominant type of highway bridge rail?

Although it's different in each state, most highway bridge rails used to contain either poles or elevated concrete slabs. Very few were just solid concrete. Then, in the mid to late 1970s (some places ...
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### Why do trains not have a high-friction emergency braking system?

Looking at the capacity of train networks, systems like CBTC help increase capacity, but the spacing of trains is ultimately limited by poor braking performance. In my understanding, safe distances ...
364 views

### What should a road's traffic volume to justify the number of lanes?

Is there a standard that transportation engineers use for the number of vehicles a road should carry daily for it to be widened to four, six, eight lanes, etc? Curious because I've noticed that some ...
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### Monorails - why even have them?

My (highly limited) engineering intuition says: Dual railing is good - for balance, for switching of tracks, for lightening load and making sure it is applied in basically the same direction always, ...
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### Why are rail signals overbuilt compared to road signals?

Here is a photo of a railroad crossing near a road intersection. Traffic, Rail Lights out of Sync at Fruitvale Avenue Crossing The road signals are mounted to slender poles (or even suspended from a ...
1 vote
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### Does the decrease in speed of the train at the curvature changes the properties of Speed Time Curve Of Urban Service

Ok, I wish to plot the speed time curve of the my urban service . The travel includes the curvature ( as shown in image ( just for reference )). The train speed is decreased while it runs along the ...
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### Vehicle load factor discrepancies

I am doing research on the impact of vehicles on roadways, specifically garbage trucks. In my research I am finding largely different "answers." For example "Using American Association of State ...
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### Why use rectifier / inverter in locomotives?

Image Source Why not just take the AC from the alternator to the motors? Why go AC to DC to AC again?
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### For train track, why does the ballast need "good drainage"?

Why does the ballast of train track need good drainage? I read something about preventing "fouling" of the ballast, but don't know what that means or why it would be structurally bad. Could ...
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### Are rocket engines practical for commercial aircraft?

What are the prospects of seeing rocket engines become the standard for commercial aircraft? It might be a dumb question; I really don't know all that much about the topic. The reason I ask is that ...
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### What's the purpose of a 'burger' lane in a roundabout?

I recently read about a newly proposed 'burger' lane across a roundabout. From what I can see, it bypasses the main point of a roundabout, a continuous circle of traffic with well defined rights of ...
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### Gate width calculation for Passenger car design vehicle

I am trying to figure out the minimum gate width required for parking a car inside the house which has a 15 feet road in front of it. Please refer to the image below: Plot is 20 feet wide. I have ...
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