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In light of the recent (Sept. 2021) power outages relating to storms and flooding, I've been thinking about a new version of a question that's been asked many times before: why not bury electrical cables when laying road?

I believe this would address multiple issues of normal underground cabling:

  1. No need to dig separate trenches. Since road is already ostensibly being laid on a suitable surface, we can simply place an undergound cabling shroud physically embedded in or directly adjacent to the road.

  2. Protection against erosion and other ground stresses. The road-embedded cabling benefits from the structural integrity of the road itself.

  3. Cables follow natural routes for power delivery. Since electricity is usually delivered to locations where there is already a road-based route leading to them, there's no need to construct new routes for underground/aboveground cabling.

  4. Easy access. Unlike a soil-buried cable, a road-buried cable could have a manhole-like detachable cover which wouldn't be swept away by erosion and could be physically anchored to road.

This seems like it would remove the major costs of cable burying and add some marginal costs to road laying. The main downsides I can think of are:

  1. the need to coordinate road-laying and cable-laying

  2. a solution to upgrade existing roads

  3. potentially much longer paths for cable to follow (although overhead lines seem to follow roads anyway)

Are there any other reasons why this wouldn't work?

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    $\begingroup$ The answer is probably "Because the USA is the USA". For example in the UK, you won't find any above-ground cables supplying domestic housing, except in very remote areas where the cost of laying say 5 miles of underground cable to supply one house would be prohibitive. $\endgroup$
    – alephzero
    Sep 2, 2021 at 17:43
  • $\begingroup$ Cables are buried or put overground. Depends on the conditions and terrain and prices. But results vary across countries… $\endgroup$
    – Solar Mike
    Sep 2, 2021 at 18:28
  • $\begingroup$ Who is going to pay for the cables ? $\endgroup$
    – blacksmith37
    Sep 2, 2021 at 18:43
  • $\begingroup$ @blacksmith37 I would imagine whomever is affected whenever the power goes out due to overhead line damage, including local customers, governments & insurance companies. $\endgroup$
    – Master Yogi
    Sep 2, 2021 at 19:08
  • $\begingroup$ Low voltage, low power, low frequency lines would be okay to bury right under the surface, aside the reasons you listed. Power transmission lines will need enough dielectric and space, thus architectural structure to support that and the load on the road as well, plus, distance (depth) from the surface due to the EMI. Thousands of voltage power lines pass right under the pavement, most of vehicles will soon stuck and glow blue on the road. Meantime, the power will be consumed to heat the road, melt metallic structures close by. After all, the cost and the risks are large and overwhelming. $\endgroup$
    – jay
    Sep 2, 2021 at 19:53

3 Answers 3

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  1. The utility company and the local government are different entities, each has its own priorities and budgets, and the life cycle of the road and utility lines usually differs, such makes coordination extremely difficult except for new development.

  2. Direct bury the powerlines underground poses a hazard for the latter roadside construction activities, routine maintenance of the lines, and system upgrade. Alternatively, it can be placed in a concrete trench box, however, place power cables in a concrete trench box is not a small issue, there are technical concerns, just to name 2 - reliving the heat (fire prevention) and flood protection. Also, there are foreseeable headaches such as damages during repaving, restrict traffic lane expansion, and more frequent/unexpected traffic interruptions due to the need to work on the cables.

  3. The design and construction efforts need to be closely coordinated which is often difficult and time-consuming, it often leads to project delays that causing the construction cost to escalate and complaints from needy customers.

There could be more though. Let's see what the others say.

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  • $\begingroup$ Great points, both (1) and (3) and ^ seem related to the common issue of coordination, upgradeability, and (possibly) multiplexing data/power/etc. Could these possibly be solved if road-based cabling had a rather generic format (like a civil eng. equivalent of USB-C PD) which electricity, data providers could pay to connect into and use? (obv would be more expensive than single-use power cables, but perhaps could be amortized against future overhead repairs..?) $\endgroup$
    – Master Yogi
    Sep 2, 2021 at 18:24
  • $\begingroup$ See @Peter W comment. Not to mention the compatibility of the different service lines, all types of utility service capacities are in constant changing mode due to changes in the local population and business vs residential ratio, so how big a trench is needed, even for the near future, is a big guessing game. Besides, I call my power company for the outage, it usually takes a few hours to fix it, but in a trench with lines placed under/next to the other services, be happy, if it can be done in a few days :) $\endgroup$
    – r13
    Sep 2, 2021 at 18:42
  • $\begingroup$ The coordinations in 1 & 3 are not directly related. In the first, the coordination is at the administrative level - one has the full budget, the other has none or a little, how to reconcile the different schedules in budgeting is an art and political matter. The coordination in the third is at the departmental levels - local government vs utility companies vs designer and, vs the contractors. The cost can be unbearably high, the project can be lengthy if one of the links is broken. I think there are better ways to express my concerns though. $\endgroup$
    – r13
    Sep 2, 2021 at 18:57
  • $\begingroup$ If these issues are a big deal, why are water and gas pipes buried, and not run above ground? It makes no sense to solve the same basic "distribution problem" in two different ways. $\endgroup$
    – alephzero
    Sep 2, 2021 at 20:55
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    $\begingroup$ " I call my power company for the outage, it usually takes a few hours to fix it" You are missing the point. In the UK nobody calls their power company for outages to underground cables, because outages don't happen. (Well, not in my personal experience. The number of outages in neighborhoods I have lived in over the last 60 years, with buried cables, has been precisely zero.) Unlike a Rube Goldberg system where every house has its own collection of failure points like poles, transformers, earthing rods, etc. $\endgroup$
    – alephzero
    Sep 2, 2021 at 21:00
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This is a biased answer, based on gripes of life experience (not as an engineer) (this by no means is the standard).

I think this is routinely done in some parts of the world.

The main drawback is what happens (in some parts of the world again) when there are problem.

What I mean is that laying the power cables under the road is something that requires a lot of technical expertise to make sure that things are done properly. When this is done, by inexperienced crews after a while you tend to have problems (it might be something like an earthquake, or just a rodent that fancied a cable that was not properly protected).

In that case:

  • problem no 1: traffic needs to be diverted to perform the necessary repairs. this means excavation, find and repairing and then redoing the road. If the road network is not properly designed, that can cause a lot of delays and anger (see "gripes" in the see first line of my post).

  • problem no.2: Sometimes (in some places of the world) the road after the repair might not be the same. As a result you might end up with roads like the following image :

enter image description here

which end up like the following:

enter image description here

Again, this is a possible downside, which is more possible in remote areas that don't have experienced or adequately qualified professionals to carry out the work.

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The fundamental reason is that at high voltages, buried cables get capacitively coupled to the surrounding earth and the buried transmission line experiences more losses per mile of run than an overhead line.

The practical reason is that it is easier to repair cables when they are overhead than when they are buried, and when overhead, they do not require a (failure-prone) insulating jacket like they do when buried.

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