Many rail lines are now electrified.

Overhead lines require gantries to support the overhead cables.

Replace existing gantries with heavy-duty steel and concrete sections and lay a 4-lane carriage way on the top.

This has many advantages.

Rail lines are well graded, and have gentel curves - ideal for a high speed limited access road.

Rail lines and workers are much more protected from weather.

Double use of existing space.

Road tolls can pay for both rail and road infrastructure.

Not recommended for areas of tectonic activity.
-- 8th of 7, Jul 26 2013

[+], although the cost of an elevated road above the tracks is probably much greater than the cost of putting a road alongside the tracks.
-- MaxwellBuchanan, Jul 28 2013


On second thoughts, bun rescinded due to the use of the phrase "Road tolls" - they are an abomination.
-- MaxwellBuchanan, Jul 28 2013


Perhaps a slight amendment to "road trolls" would be more acceptable to m'lord?
-- AusCan531, Jul 28 2013


Toad rolls anyone? The anagram engine comes up with "Dollars To" and "Lard Stool".
-- not_morrison_rm, Jul 28 2013


anagram engine gave: Searchlight away kid! for this idea.
-- pashute, Jul 29 2013


What happens at bridges and tunnels?
-- xenzag, Jul 29 2013


// putting a road alongside the tracks. //

This is a space-saving idea ... road OVER rail, not next to it. That's very Baked.

// bun rescinded due to the use of the phrase "Road tolls" - they are an abomination. //

"Road tolls can pay for both rail and road infrastructure" will be replaced by "Massively increased taxes on the less well off can pay for both rail and road infrastructure"

// What happens at bridges and tunnels //

Tunnels; a second boring above the first.

Bridges; a gentle gradient up to and down from a flyover.
-- 8th of 7, Jul 29 2013


Road usage fees are hardly an abomination. You're still paying for it one way or another, better to pay for what you're actually using.
-- MechE, Jul 29 2013


What are the chance of electric getting loose and toasting cars and occupants?

Hard to imagine how to commit suicide using the electric cable. like one can with a third rail.

What would be a good estimate of the cost savings?

Unless you've brand new city the old road will still be there for local traffic or long and narrow parks.
-- popbottle, Jul 29 2013


// What are the chance of electric getting loose and toasting cars and occupants? //

Fair to good. Your point is ... ?

// Hard to imagine how to commit suicide using the electric cable. like one can with a third rail. //

1. Attach a small, heavy metal object to a 6m length of medium grade uninsulated flexible copper wire. Bind other end of wire firmly around left wrist.

2. Remove shoes and socks. Stand on rail.

3. Throw small, heavy metal object over catinery cable and wait for wire to make contact.

Go on, go out and try it. Please. You'll be surprised how easy it is, and how well it works. We hope.
-- 8th of 7, Aug 01 2013


//This is a space-saving idea// But the one thing we still have plenty of is space. All the humans on earth could stand shoulder to shoulder on the Isle of Wight.

1.2% of the UK is covered by roads, and another 0.02% by rail. 0.7% of the USA is covered by roads.

We don't need the extra space. And if we did, it would be far, far cheaper to engineer a plague and reduce the roadgoing population than it would to build over-rail roads.

In fact, the most economical mid-term solution to almost all envirosocial problems (global warming; lack of fresh water; pollution; energy shortage; urban overcrowding; food shortages; housing shortages; deforestation; overfishing etc etc) would be a really good plague. Or a really effective war - war is environmentally very friendly.
-- MaxwellBuchanan, Aug 05 2013



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