# Should NY Subway Tracks \[be\] Clogged w/ Corpses of Rats who Touched the Third Rail? **URL:** \ **Category:** Factual Questions\ **Created:** [May 16, 2009, 1:51pm UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638 "2009-05-16T13:51:30Z")\ **Posts on this page:** 13\ **Page:** 3
**Author:** ![Kiwi\_Fruit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kiwi_fruit/32/12_2.png) [@Kiwi\_Fruit](https://boards.straightdope.com/u/Kiwi_Fruit)\ **Post date:** [May 17, 2009, 11:59pm UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/41 "2009-05-17T23:59:01Z")
> [@mangeorge](#): > > I’ve heard of this too, but I’ve been unable to find _any_ examples. > I worked as an electrician for many (30) years, first in construction then maintenance. Then I came to a much easier way to make a living as a tech. So I’ve been around electricity a lot, both high and low voltage, and would surely have encountered the practice of using earth as a conductor if such a practice existed. Plus I’ve done some research. Nada. Except for the unlikely comparison to radio transmission, all circuits use a return wire. > A big fat virtual hug (manhug) to anyone who can show me. > Peace, > mangeorge I think [this](http://en.wikipedia.org/wiki/Single_wire_earth_return), known as SWER, may be what you’re looking for. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 18, 2009, 12:16am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/42 "2009-05-18T00:16:49Z")
> [@Kiwi\_Fruit](#): > > I think [this](http://en.wikipedia.org/wiki/Single_wire_earth_return), known as SWER, may be what you’re looking for. OK, this kinda thing makes absolutely no sense to me. I get the idea of using the earth to complete a circuit, sorta, but we’re talking about dirt and rocks vs. solid copper. How can you do this without losing 99% of your current to resistance? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 18, 2009, 12:21am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/43 "2009-05-18T00:21:39Z")
> [@](#): > > But that’s for a low resistance DC circuit, where you have a good conductor for the entire circuit. What happens to the slow-poke electrons if you lift the negative (grounded) conductor at the source? When you break the circuit, electrons throughout the circuit all stop moving (almost) simultaneously: The signal propagation speed is the speed of light in the wires. But the electrons themselves are still moving very slowly. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [May 18, 2009, 1:12am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/44 "2009-05-18T01:12:51Z")
> [@Kiwi\_Fruit](#): > > I think [this](http://en.wikipedia.org/wiki/Single_wire_earth_return), known as SWER, may be what you’re looking for. Here it comes, unh, unh, unh, unh, how was that? I didn’t squeeze too hard, I hope. 😛 I’ll read the whole thing after I eat. And thanks. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [May 18, 2009, 1:17am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/45 "2009-05-18T01:17:58Z")
> [@friedo](#): > > OK, this kinda thing makes absolutely no sense to me. I get the idea of using the earth to complete a circuit, sorta, but we’re talking about dirt and rocks vs. solid copper. How can you do this without losing 99% of your current to resistance? Well, the article mentioned that each ground needed to be under 10Ω or so. This is on the Primary (high voltage) side, so the current is relatively low. If the primary was carrying 8A, then you would lose 64\* 10 = 640W of power in the ground connection, which is significant, but not huge. ---
**Author:** ![Kiwi\_Fruit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kiwi_fruit/32/12_2.png) [@Kiwi\_Fruit](https://boards.straightdope.com/u/Kiwi_Fruit)\ **Post date:** [May 18, 2009, 1:52am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/46 "2009-05-18T01:52:14Z")
> [@friedo](#): > > OK, this kinda thing makes absolutely no sense to me. I get the idea of using the earth to complete a circuit, sorta, but we’re talking about dirt and rocks vs. solid copper. How can you do this without losing 99% of your current to resistance? I should have linked to [RuralPower.org](http://www.ruralpower.org/index.php?option=com_content&view=article&id=19:swer-and-rural-electrification-downloads&catid=11:swer-and-rural-electrification-downloads&Itemid=9) to start with. It’s the background information by one of the developers of the system. There’s a big PDF (7Megs) which is a scanned document written by Lloyd Mandeno. The system is used extensively in NZ and Australia and other places around the world. The earthing is easier to do in moist climates such as NZ, but obviously does work in drier places as well. Even in Alaska, as long as the earthing is beneath the permafrost, it works. Permafrost has very high resistance, so it does cause problems. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [May 18, 2009, 3:43am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/47 "2009-05-18T03:43:10Z")
> [@friedo](#): > > OK, this kinda thing makes absolutely no sense to me. I get the idea of using the earth to complete a circuit, sorta, but we’re talking about dirt and rocks vs. solid copper. How can you do this without losing 99% of your current to resistance? Don’t forget that while dirt and rocks may have high resistance compared to copper, you are talking about a copper wire at most an inch or so across, while the dirt-and-rock “wire” is potentially enormous in effective cross section. ---
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [May 18, 2009, 5:22am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/48 "2009-05-18T05:22:21Z")
> [@Princhester](#): > > Don’t forget that while dirt and rocks may have high resistance compared to copper, you are talking about a copper wire at most an inch or so across, while the dirt-and-rock “wire” is potentially enormous in effective cross section. Sorry for the nitpick here, but the word you should use there is “resistivity”. Resistance already takes into account the cross-sectional area; resistivity is an inherent property of the material independent of its shape. ---
**Author:** ![coffeecat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/coffeecat/32/3405_2.png) [@coffeecat](https://boards.straightdope.com/u/coffeecat)\ **Post date:** [May 18, 2009, 11:05am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/49 "2009-05-18T11:05:21Z")
A tesla coil? I’m walking barefoot through the grass, and a power line falls on my head? 😛 And what are the capacitance and resistance of your average rat? How about the inductance? Does it make a difference if its tail is curled into a spiral? Can we figure out a way to make a radio entirely out of rats? That sounds like a Doper project on a par with the goat cannon, and a real conversation starter if we can make it work. ---
**Author:** ![Umbriel2](https://avatars.discourse-cdn.com/v4/letter/u/4af34b/32.png) [@Umbriel2](https://boards.straightdope.com/u/Umbriel2)\ **Post date:** [May 18, 2009, 6:26pm UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/50 "2009-05-18T18:26:23Z")
My theory: Rats, living largely in the dark, make extensive use of their whiskers in exploring their environment. I would think that a rat, before attempting to climb a third rail, would likely touch it with its whiskers. That would either singe the whiskers or otherwise give the rat a painful, but non-lethal, reason to avoid future contact with a third rail. The same principle might apply to rats’ fur generally – providing them with a semi-insulating coat that makes it less likely that they’ll make good enough contact to suffer a dangerous jolt. None of these are perfect defenses, of course, and you do sometimes hear about rodent-induced electrical fires, but it does provide an explanation of why the rat toll isn’t far higher. ---
**Author:** ![Reno\_Nevada](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@Reno\_Nevada](https://boards.straightdope.com/u/Reno_Nevada)\ **Post date:** [May 18, 2009, 7:05pm UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/51 "2009-05-18T19:05:06Z")
> [@Markxxx](#): > > I’m sure rats eat each other if they are dead. Man. CHUDs, albino alligators, and now ZOMBIE RATS! I am amazed anyone at all survives a NY subway ride. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [May 18, 2009, 10:07pm UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/52 "2009-05-18T22:07:19Z")
> [@Reno\_Nevada](#): > > Man. CHUDs, albino alligators, and now ZOMBIE RATS! I am amazed anyone at all survives a NY subway ride. I think **Markxxx** needs to re-read his post. 😛 ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [May 19, 2009, 7:51am UTC](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638/53 "2009-05-19T07:51:41Z")
> [@DrCube](#): > > Sorry for the nitpick here, but the word you should use there is “resistivity”. Resistance already takes into account the cross-sectional area; resistivity is an inherent property of the material independent of its shape. Don’t be sorry. I knew I needed a term that meant that, but didn’t realise it existed, thanks. [Previous page](https://boards.straightdope.com/t/should-ny-subway-tracks-be-clogged-w-corpses-of-rats-who-touched-the-third-rail/496638.md?page=2)