# Intersections in tunnels **URL:** \ **Category:** Factual Questions\ **Created:** [December 8, 2020, 9:49pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599 "2020-12-08T21:49:35Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [December 15, 2020, 5:40am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/41 "2020-12-15T05:40:14Z")
The talk about fires in tunnels reminded me of a bad one here in the SFBA CA about 40 years ago: Anatomy of a disaster: [The 1982 Caldecott Tunnel fire that killed seven](https://www.mercurynews.com/2013/10/29/anatomy-of-a-disaster-the-1982-caldecott-tunnel-fire-that-killed-seven/). There’s a wiki page for it, [Caldecott Tunnel fire](https://en.m.wikipedia.org/wiki/Caldecott_Tunnel_fire). It started with a drunk driver with a BAC of 0.17% and led to a gasoline tanker truck exploding. The explosion and massive flames shot out the end of the tunnel. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2020, 7:20am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/42 "2020-12-15T07:20:12Z")
> [@Telemark](#): > > In New England (where I grew up and still live) we call them “rotaries” and the rule is always “Traffic in the rotary has the right of way”. I’m sorry but this is not correct. That’s the rule in modern roundabouts and many rotaries have been converted to that rule, but it isn’t the original rule for them. As far as I can tell, rotaries favor traffic entering on two of the legs, basically making it a continuation of an arterial. Those two legs do not have yield signs at their entrance but traffic already in the rotary get yield signs giving those two entrances the right of way. That’s right, traffic already in the rotary does not always have right of way. I’ve seen this on a number of rotaries; I can give you googlemap links if you want them. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [December 15, 2020, 12:52pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/43 "2020-12-15T12:52:03Z")
> [@dtilque](#): > > That’s the rule in modern roundabouts and many rotaries have been converted to that rule, but it isn’t the original rule for them. As far as I know, that is the rule in Massachusetts and all the New England states. It’s why there are Yield signs at every entrance. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [December 15, 2020, 5:41pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/44 "2020-12-15T17:41:12Z")
> [@dtilque](#): > > That’s the rule in modern roundabouts and many rotaries have been converted to that rule, but it isn’t the original rule for them. Here’s a cite for that: > **[What is a Roundabout](https://portal.ct.gov/DOT/Highway-Design/What-is-a-Roundabout)** ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2020, 8:42pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/45 "2020-12-15T20:42:10Z")
> [@Telemark](#): > > As far as I know, that is the rule in Massachusetts and all the New England states. It’s why there are Yield signs at every entrance. Here’s an [example of a rotary](https://www.google.com/maps/@42.32247,-71.1378665,3a,75y,35.21h,90t/data=!3m7!1e1!3m5!1s4AXy8TMUhggm47WFcDxtJQ!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3D4AXy8TMUhggm47WFcDxtJQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D141.90636%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) with a yield sign aimed at the traffic in the circle. No yield sign for the entering traffic. This one is in Brookline MA. Here’s another in [Stratham NH](https://www.google.com/maps/@43.0215562,-70.9167134,3a,75y,93.4h,90t/data=!3m7!1e1!3m5!1sE08VV4IAvdnwZvZrNWrLNw!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DE08VV4IAvdnwZvZrNWrLNw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D238.71654%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656). Just want to note that most rotaries do have yield signs at all the approaches. As I said above, they’ve been converted to that. They weren’t always that way. It’s only after roundabouts showed that that was the best way to control circular intersections that they converted them. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [December 15, 2020, 9:01pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/46 "2020-12-15T21:01:44Z")
> [@dtilque](#): > > Here’s an [example of a rotary](https://www.google.com/maps/@42.32247,-71.1378665,3a,75y,35.21h,90t/data=!3m7!1e1!3m5!1s4AXy8TMUhggm47WFcDxtJQ!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3D4AXy8TMUhggm47WFcDxtJQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D141.90636%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) with a yield sign aimed at the traffic in the circle. No yield sign for the entering traffic. This one is in Brookline MA. Bringing up those coordinates at [Historic Aerials: Viewer](https://www.historicaerials.com/viewer) shows that circle goes back to at least 1938. > [@dtilque](#): > > Here’s another in [Stratham NH](https://www.google.com/maps/@43.0215562,-70.9167134,3a,75y,93.4h,90t/data=!3m7!1e1!3m5!1sE08VV4IAvdnwZvZrNWrLNw!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DE08VV4IAvdnwZvZrNWrLNw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D238.71654%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656). '62 for this one. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2020, 9:48pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/47 "2020-12-15T21:48:41Z")
> [@Skywatcher](#): > > '62 for this one. I’m somewhat surprised they built a rotary that late. I’d always heard that they fell out of favor in the 1950s. But you did say “at least”, so perhaps it was built a few years earlier. Modern rounabouts were not invented until 1966. That is when the rule to always yield to traffic in the circle was introduced. They also changed other things about circular intersections, such as making them smaller. But because rotaries had gotten such a bad rep in North America, roundabouts weren’t introduced in this part of the world until 1988. That one was in what is now Elk Grove CA, a suburb of Sacramento. But that one flew under the radar; it’s usually written that the first modern roundabouts in the US were two in Summerlin NV (large subdivision in Las Vegas) in 1990. Not that it makes much difference. Roundabouts took a while to catch on; there were only a couple hundred in the entire US by the turn of the century. Then they started to take off. Nowadays they build 450-500 every year. In Canada, the first roundabout was one in Montreal in 1998. They now build 60-70 every year. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [December 15, 2020, 10:05pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/48 "2020-12-15T22:05:59Z")
> [@dtilque](#): > > I’m somewhat surprised they built a rotary that late. I’d always heard that they fell out of favor in the 1950s. But you did say “at least”, so perhaps it was built a few years earlier. Topographic maps show it was there in '58. I originally didn’t bother looking at early topo maps because they didn’t show the circle for Brookline. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [December 15, 2020, 10:36pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/49 "2020-12-15T22:36:03Z")
[There’s a rotary near here](https://en.wikipedia.org/wiki/Shirlington,_Arlington,_Virginia#Shirlington_Circle) which was originally built in '49 – along with the highway – and was enlarged in the early Seventies. ---
**Author:** ![Mark\_Finn](https://avatars.discourse-cdn.com/v4/letter/m/34f0e0/32.png) [@Mark\_Finn](https://boards.straightdope.com/u/Mark_Finn)\ **Post date:** [December 16, 2020, 1:15pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/50 "2020-12-16T13:15:22Z")
Montreal (Canada) has a “traffic circle” well-known to locals. Built in 1939 on a “new” divided highway, an overpass was built in the 60s allowing through traffic to go over it. There was still so much traffic on the original circle (and drivers never knew who was supposed to yield) that they eventually put in four traffic lights - one for each intersection. Original: [http://johnxxiiihighschooldorvalqc.weebly.com/uploads/1/0/0/7/10079709/\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_4246583\_orig.jpg](http://johnxxiiihighschooldorvalqc.weebly.com/uploads/1/0/0/7/10079709/ __________________________________ 4246583_orig.jpg) Today (rotated 180 degrees from the other image): [https://beta.ctvnews.ca/content/dam/ctvnews/images/2020/10/21/1\_5153913.jpg?cache\_timestamp=1603277898539](https://beta.ctvnews.ca/content/dam/ctvnews/images/2020/10/21/1_5153913.jpg?cache_timestamp=1603277898539) ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [December 16, 2020, 2:09pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/51 "2020-12-16T14:09:56Z")
> [@dtilque](#): > > Here’s an [example of a rotary](https://www.google.com/maps/@42.32247,-71.1378665,3a,75y,35.21h,90t/data=!3m7!1e1!3m5!1s4AXy8TMUhggm47WFcDxtJQ!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3D4AXy8TMUhggm47WFcDxtJQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D141.90636%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) with a yield sign aimed at the traffic in the circle. No yield sign for the entering traffic. This one is in Brookline MA. That intersection looks like the illegitimate child of a roundabout and a [Michigan left](https://en.wikipedia.org/wiki/Michigan_left). No one has ever accused Massachusetts of having rational and consistent traffic laws. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [December 16, 2020, 3:02pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/52 "2020-12-16T15:02:33Z")
There are several rotaries in Washington, D.C. that, I think, may date back to the founding of the city. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [December 16, 2020, 3:16pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/53 "2020-12-16T15:16:43Z")
> [@Marvin\_the\_Martian](#): > > [Michigan left](https://en.wikipedia.org/wiki/Michigan_left). I’m surprised they only mention two in Texas; these are all over Houston, wherever a highway service road crosses a major street. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [December 16, 2020, 4:09pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/54 "2020-12-16T16:09:14Z")
> [@dtilque](#): > > Here’s an [example of a rotary](https://www.google.com/maps/@42.32247,-71.1378665,3a,75y,35.21h,90t/data=!3m7!1e1!3m5!1s4AXy8TMUhggm47WFcDxtJQ!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3D4AXy8TMUhggm47WFcDxtJQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D141.90636%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) with a yield sign aimed at the traffic in the circle. No yield sign for the entering traffic. This one is in Brookline MA. Here’s another one in [Somerville](https://www.google.com/maps/@42.4092789,-71.1306118,3a,75y,197.42h,87.4t/data=!3m6!1e1!3m4!1sVKsdBUBu2ns2-JYpZ1fa0Q!2e0!7i16384!8i8192) in which traffic westbound on Rt 16 has the right of way entering the rotary, but traffic eastbound must yield. Nothing like consistency. Welcome to Massachusetts! ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [December 16, 2020, 4:22pm UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/55 "2020-12-16T16:22:41Z")
Swindon, England has [this](https://en.wikipedia.org/wiki/Magic_Roundabout_(Swindon)) [crazy](https://www.bbc.com/news/uk-england-wiltshire-19726385) [roundabout](https://www.youtube.com/watch?v=D22BOOGbpFM); five very small roundabouts around a large one. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [December 17, 2020, 5:29am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/56 "2020-12-17T05:29:50Z")
There must be some sort of international road-design-crimes treaty against such abominations. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 17, 2020, 6:00am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/57 "2020-12-17T06:00:08Z")
> [@Elendil\_s\_Heir](#): > > There must be some sort of international road-design-crimes treaty against such abominations Which abominations do you mean? The ones with yield signs in them or that “magic” roundabout in Swindon? The former are grandfathered in; the latter should be nuked from orbit. Anyway, lest someone get the idea that only non-circular rotaries have yield signs in them or they are just in the US, here’s a circular one in [Hamilton, Ontario](https://www.google.com/maps/@43.2374196,-79.8008606,3a,75y,104.69h,90t/data=!3m6!1e1!3m4!1sZow-JLBgLgkxOrSGsNNOow!2e0!7i16384!8i8192). It’s one of two such in that city. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 17, 2020, 7:56am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/58 "2020-12-17T07:56:52Z")
Don’t want to leave New Jersey out (they’re as guilty as Massachusetts): [one in Lawrence Township, NJ](https://www.google.com/maps/@40.2454092,-74.7421899,3a,75y,335.21h,90t/data=!3m6!1e1!3m4!1s5mjfGG_PqI83uAOJMrULGw!2e0!7i16384!8i8192). ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [December 17, 2020, 8:55am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/59 "2020-12-17T08:55:10Z")
It’s amusing to see how this thread has evolved into a “What’s the weirdest roundabout you have ever seen?” collection. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 17, 2020, 9:56am UTC](https://boards.straightdope.com/t/intersections-in-tunnels/927599/60 "2020-12-17T09:56:33Z")
Actually, these are mostly rotaries, which are a different animal than roundabouts. Besides having yields within the circle, rotaries are generally much bigger than roundabouts.[\*] There’s an example of a rebuild of a rotary into a roundabout [here (go to the 4th slide)](https://www.slideshare.net/kaiblog/kai-modern-urban-roundabouts)[\*\*]. The outer circle is the rotary, about 600 ft (180 meters) across. The inner circle is the roundabout 190 ft (58 meters) across. They’ve since removed the outer circle, as you can see [here (Kingston NY)](https://www.google.com/maps/place/Kingston,+NY+12401/@41.9435925,-74.0285406,298m/data=!3m1!1e3!4m5!3m4!1s0x89dd0f012dc98127:0x41d7895a5832c913!8m2!3d41.9270367!4d-73.9973608) . [\*] Another difference was how you drove through them. Rotaries often require lane changes if they have more than one lane. You should stay in the same lane when driving a multi-lane roundabout. [\*\*] Sorry about the slide thing, but the only other examples of this picture I could find were in PDFs. [Previous page](https://boards.straightdope.com/t/intersections-in-tunnels/927599.md?page=2) [Next page](https://boards.straightdope.com/t/intersections-in-tunnels/927599.md?page=4)