27 votes
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What are the pros and cons of a traffic circle versus a traffic light intersection?

I think you are talking about roundabouts, not traffic circles. It is baffling to those of us in the UK that Americans think roundabouts are a new idea. In the UK we have so many variants, from mini-...
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  • 5,930
18 votes

Why do we pave roads instead of making them from removable parts?

This is very common misunderstanding. When we look a a road, we see few centimeters thick layer of bituminous surface, and we think about "the road" as "the asphalt/tarmac." It's not. When you look ...
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  • 416
18 votes
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Why was a coil chosen over a straight for this overbridge?

source google maps The distance between the intersection and the rail is 100m, The road would need to rise about 10m to clear the track. This would mean a average grade of 10%. However you also need ...
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14 votes

What are the pros and cons of a traffic circle versus a traffic light intersection?

There's a hierarchy of junctions, that you'll find in most standard highway design guides, such as the UK's immense Design Manual for Roads and Bridges. Different junction designs have different ...
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  • 3,701
13 votes
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What is the justification for working on such large stretches of road?

I'll give you some considerations that you may not be aware of. Also, take the disclaimer that I'm in the US (but construction is construction, right?) Frequently moving construction cones/barrels ...
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12 votes
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What is a Spiral Curve, and How is it Different from a Normal Curve?

Spiral A spiral curve is a geometric feature that can be added on to a regular circular curve. The spiral provides a gradual transition from moving in a straight line to moving in a curve around a ...
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11 votes

What are the pros and cons of a traffic circle versus a traffic light intersection?

Roundabout: Pros As you've mentioned, the Mythbusters' test results showed that roundabouts were about 20% more efficient for cars, good for high traffic Allows more cars to cross at a time. Doesn'...
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  • 301
9 votes

What is a Spiral Curve, and How is it Different from a Normal Curve?

It isn't a question of being "aesthetically pleasing to the eye", but rather of comfort. If you had a curve that was simply a circular arc, upon entering that curve, you would immediately feel a ...
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  • 6,749
9 votes
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Has a specific type of alternative intersection been shown to reduce congestion & accidents?

Yes. Michigan left This page (pdf here) is very informative, though you really have to dig to get what you want. In a sub-section of 10.2.2 Median U-Turn Crossover, I found this (A "Michigan left" ...
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  • 2,485
9 votes
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What's sort of "sidewalk" pavement is this?

The technical term for this (in the UK) is "deterrent paving" and its function is to discourage pedestrians, cyclists and drivers from being where they are not supposed to be. In the OP's photo, the ...
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  • 12.5k
8 votes

What are the pros and cons of a traffic circle versus a traffic light intersection?

Like the British, Australia has had roundabouts for at least five decades in some shape or form and there prevalence has increased over the last thirty years or so. In the city were I live there is a ...
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  • 9,447
8 votes

Why do we pave roads instead of making them from removable parts?

You mean going back to cobblestone roads? Many sidewalks are often paved with pavers. One of the challenges is maintaining a level surface. Asphalt holds itself together like a sheet and a dip in the ...
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7 votes
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What would be the implications of a metal highway design?

Asphalt, which is essentially crushed aggregate bound with bitumen has a lot of advantages for road building. It is porous and so can drain by allowing water to pass through it as well as running ...
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7 votes

Why do we pave roads instead of making them from removable parts?

I think that there are a few things that you aren't considering. Subgrade Most roads have at least 12 in (300 mm) of compacted aggregate (rock) under the actual pavement. If the existing soil is very ...
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  • 10.6k
7 votes

Does passenger car traffic actually damage roads?

Yes, there would be a noticeable difference. Normal passenger cars don't really stress the road surface much. That's not so much the issue. As a analogy, you can have 100 people walk across a small ...
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  • 11.2k
7 votes
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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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  • 10.6k
6 votes

What are the pros and cons of a traffic circle versus a traffic light intersection?

Roundabouts are only good for equal distribution of incoming traffic. As soon as one road feeds more traffic it will starve the other roads. Small roundabouts are less efficient than large ones. So ...
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6 votes
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Why are roads straightened when widened?

A wider road will have faster average traffic speeds, because faster vehicles will be hindered less by slow ones, with more lanes available for overtaking. So longer visibility distances are needed ...
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5 votes

How are earthfills not eroded before they are overgrown with grass?

The slope angle of such slopes is constructed to be less than the angle of repose for the material used in the slope. The angle of repose is the great angle to which granular materials can be dumped ...
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  • 9,447
5 votes

How are earthfills not eroded before they are overgrown with grass?

There are a few methods that are used to control erosion before permanent vegetation is established. The exact method used can depend on location (also country), season, preference, governing laws, ...
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5 votes

What kind of splines should be used when planning roads?

Circular arcs are not used except in special situations, because the sudden change in curvature from a straight road to a circular arc would mean drivers had to quickly turn the steering wheel to the ...
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5 votes

What kind of splines should be used when planning roads?

Roads are usually designed using catenary curves. https://sketchup.engineeringtoolbox.com/catenery-curve-c_169.html Road curves are designed around vehicle velocities and they are not uniform. As ...
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  • 844
4 votes

How are earthfills not eroded before they are overgrown with grass?

They lay turf pads down to kickstart the grass coverage. Even the loose pads will have better erosion protection than bare soil. Other options include laying down a sheet with holes for plants/...
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4 votes

Why do we pave roads instead of making them from removable parts?

As some of the other posters have mentioned a road has several built up layers (hopefully). The drainage system is usually very important. Bad quality roads are usually because the drainage is poor or ...
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  • 1,605
4 votes
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Best traffic control device/system for given situation

A round-a-bout introduces a disruption in any traffic, no matter which direction. In your case the only two "collision" directions - two left turns - are the least used ones, so traffic lights ...
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  • 6,123
4 votes

What are the pros and cons of a traffic circle versus a traffic light intersection?

People using the road make mistakes (like running stop signs and red lights), always have and always will. Crashes will always be with us, but they need not result in fatalities or serious injury. ...
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4 votes

How much noise does a road noise barrier block?

The US Federal Highway Administration says: Effective noise barriers can reduce noise levels by 10 to 15 decibels, cutting the loudness of traffic noise in half. It goes on to say that a 5 dB ...
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  • 141
4 votes

Does the speed of Heavy Vehicles make more potholes

Vertical loading does (almost) nothing to a properly designed and constructed bitumen road surface, it is horizontal loading that causes deterioration. Horizontal loading comes from acceleration, ...
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  • 3,145
4 votes
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NASCAR corners on public roads

Public roads must be safe to handle slow, heavy traffic and be safe to pull over a stalled car under a snow storm. They should be flat enough to make it easy for emergency services such as ambulances,...
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  • 21k
4 votes
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Permanent uneven deformation of asphalt car park under portable cabins

I wouldn't expect this to be a big problem. Would you be worried about leaving a car parked in one place on this pavement for a month? Typical car tire pressures are at least 2 bar or 200 kN/m^2, ...
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