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I'm cycling around Japan, and a few days ago I cycled the Shimanami Kaido, a series of bridges connecting islands between the mainland and Shikoku in the inland sea. One of the bridges there was (if I recall correctly) 6.5km long. This had a specially made bicycle/pedestrian/moped section.

I also have come across several tunnels, the longest of which was 2.8km, on route 317 on a mountain pass between Matsuyama and Imabari. There wasn't a specific cycle path there per se, but there was a sufficiently large raised path on one side so that I was perfectly safe (that said, there were areas where the lights had blown and I was cycling in pitch black!).

This got me thinking. What are the longest tunnels and bridges that are safe for cyclists to cross/pass through? I'll add the extra condition that it must not be specifically illegal.

JoErNanO
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Bamboo
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    There are some pretty long dikes in the Netherlands that have separated cycle lanes (eg. Afsluitdijk, about 25 km). Does that count as a bridge? – Greg Hewgill Jun 05 '19 at 03:26
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    Chris Froome was once allowed to cycle through the Channel Tunnel's service tunnel. That's about 50 km. I suspect, though, that you're looking for tunnels open for anyone to cycle through. – Michael Hampton Jun 05 '19 at 05:15
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    @GregHewgill the Afsluitdijk is actually 32km long. But there are renovations going on meaning that for quite a while the bicycle path will be closed. – Paul Palmpje Jun 05 '19 at 06:04
  • Can you clarify what counts as "longest" for you, single spans or total distance? Are causeways and dikes OK? – lambshaanxy Jun 05 '19 at 06:54
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    @jpatokal, since the question mentions a 6.5 km bridge I think we can safely infer that it's not asking for single spans. – hmakholm left over Monica Jun 05 '19 at 11:06
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    @jpatokal several spans is ok, the main idea is that it's some kind of continuous structure holding a roadway above the ground – Bamboo Jun 05 '19 at 11:29
  • Does the bridge have to be open to cycling at any time, or do regular special events count? Some bridges have special events where they're open to cyclists or pedestrians one day out of the year. – Michael Seifert Jun 05 '19 at 14:48
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    Honourable mention - not the longest at just over 2km but >200m up: The Pont de Normandie. The downside is the bike path is only separated from the Autoroute by paint; most similar bridges have a solid fence. Heights make me nervous - I want to try it. – Chris H - UK Jun 05 '19 at 14:59
  • I believe there is a bridge in China that is long enough for a marathon? I'm not sure about the details of the roadway though. – Michael Richardson Jun 05 '19 at 18:50
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    @MichaelRichardson, there are plenty of long bridges out there. The question is which ones permit bicycles (the world's longest bridge, for example, is trains-only). – Mark Jun 05 '19 at 20:09
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    @CrisH: are you going to cycle the cables? Otherwise I guess you'll be only maybe 60 m above the sea... – cbeleites unhappy with SX Jun 06 '19 at 17:14
  • Have it to be public road for daily use? Or could it be on special events too? If so, you could look at my answer for the mine "Merkers" in Germany – Allerleirauh Jun 07 '19 at 09:46
  • @cbeleites you're right - 52m to the deck. Still a long way down. I've only been over it as a passenger in a car – Chris H - UK Jun 07 '19 at 10:38
  • @ChrisH Being so close to high speed traffic makes me nervous about going up that bridge! The hard shoulder is very narrow and almost nonexistent in places. But it should be possible to reach 70+ coming down the other side, so you can probably just take a lane. – Michael Hampton Oct 17 '19 at 21:43
  • The 水ヶ峠トンネル (The tunnel you reference, not sure in the reading) is 2.08km long not 2.8km – paullb Nov 12 '19 at 22:45

9 Answers9

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The Seven Mile Bridge in the Florida Keys is open to cyclists. The Florida Keys Overseas Heritage Trail, a nearly-complete 106 mile (171 km) cycling path from Key West to Key Largo, and part of the East Coast Greenway which stretches to the Maine-Canada border, is routed over the bridge. (The bridge is actually 10.9 km or 6.8 miles long.)

Michael Hampton
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Not a bridge or a tunnel, but as a bonus, consider the Afsluitdijk, a 32 km artificial enclosure dam and causeway connecting the Dutch provinces Noord-Holland and Friesland, separating IJsselmeer from Waddenzee. As a causeway, I'd argue it's somewhat similar to bridges and tunnels, in that it connects two landmasses otherwise separated by water. Enjoy cycling it, in particular with a strong headwind.

afsluitdijk
Source: C.S. Brooms/Kris Rodenburg, Rijksdienst voor het Cultureel Erfgoed, via Wikimedia Commons

gerrit
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    Nice, I like it! I was thinking of man made structures in general, but I could only think of bridges and tunnels – Bamboo Jun 05 '19 at 11:31
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    While the Afsluitdijk is closed, you can try the similar Houtribdijk between Lelystad and Enkhuizen. When they're both open, you can do both in the same day, if you start reasonably early, as I did (and I am a rank amateur at cycling). – Robert Furber Jun 05 '19 at 11:39
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    @Abigail Well, yes, but it doesn't resemble a bridge unless it has water on both sides and connects two pieces of land, I think. – gerrit Jun 05 '19 at 13:06
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    @Abigail I think it's pretty clear that the question is not asking "What is the longest road that can be cycled on." That question would be almost nonsensical. – David Richerby Jun 05 '19 at 15:52
  • There are a few impressive dikes (with water on both sides) in Zeeland (south west in the Netherlands,) but non as long as the Afsluitdijk. – Willeke Jun 05 '19 at 15:53
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Most of the world's longest road tunnels are on express- or motorways, where cycling is prohibited anyway, independent of the tunnel.

The longest road tunnel I could find, which is definitely open for bicyclists is the 8,079m long Steigen Tunnel in Norway.

I would however also assume that bicycling is allowed in the 14,346m long Mount Ovit Tunnel in Turkey. I can't find any specific information about bicycling in this tunnel, but the road is designated as a regular highway (not a motorway) and bicycling is generally allowed on Turkish highways, even on 4-lane highways.

If it is safe or not is a matter of taste. In any tunnel, even very short tunnels, passing vehicles may cause severe and difficult to predict draughts, which can be tedious to cope with when bicycling. Most longer tunnels also have a cold, moist and uncomfortable climate.

Completely safe alternatives, but not nearly as long, are all the tunnels along the decommissioned railway lines, which have been rebuilt as pedestrian or bicycle paths in many countries over the past few decades. In Europe, the 2,630m long Uitzi Tunnel in Spain is probably the longest. I am not sure if it is currently open, as it has been frequently closed during the last years for maintenance or because of water leaks.

Tor-Einar Jarnbjo
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    "[A] cold, moist and uncomfortable climate" That's the day-to-day experience of 60 million people in the UK. We survive. – David Richerby Jun 05 '19 at 15:51
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    Good point about the drafts from passing vehicles. When I was thinking of safety, I was mainly thinking "do I have to worry about being hit by a truck trying to pass me?" – Bamboo Jun 05 '19 at 15:59
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    I would not recommend cycling in a long road tunnel without a pavement/sidewalk. Some Norwegian road tunnels, such as the North Cape Tunnel (6.9 km, -212 m) have a pavement, so cycling is safe (I assume cycling on the pavement is permitted). – gerrit Jun 05 '19 at 16:02
  • @gerrit It is in Norway allowed to cycle on pavements/sidewalks, but pedestrians have the 'right of way' and cyclists must yield for them. Draught from passing vehicles is the same problem even if the tunnel happens to have a sidewalk, so I am not sure if that helps. At least in Norway, many tunnels have slanted and/or very rough walls, so it is often difficult to bicycle close enough to the tunnel wall anyway. – Tor-Einar Jarnbjo Jun 05 '19 at 16:37
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    About the Mount Ovit tunnel, from the few pictures I was able to find, there doesn't seem to be enough space in there for a cyclist to pass through safely, with vehicles giving any significant amount of clearance. I don't think I would want trucks passing by close enough to touch at 80 km/h. – Michael Hampton Jun 05 '19 at 17:14
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    @MichaelHampton From my little experience of bicycling in Turkey, car drivers are much more considerate than one would perhaps assume. There won't be heavy traffic in the tunnel and if you simply use the right lane for cycling, cars will overtake you in the left lane. That strategy worked at least perfectly on the highway from Edirne to Istanbul with many stretches built like this: https://www.google.de/maps/@41.6422347,26.6033178,3a,75y,152.43h,84.4t/data=!3m5!1e1!3m3!1sRyyMiKLvojyYOTOSd0gJDA!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3DRyyMiKLvojyYOTOSd0gJDA – Tor-Einar Jarnbjo Jun 05 '19 at 19:27
  • @Tor-EinarJarnbjo There's a "share the road" sign in that street view image! But your point is well made. In some countries (like the USA) a lot of car drivers are very unhappy sharing the road with cyclists. – Michael Hampton Jun 06 '19 at 00:30
  • @Tor-EinarJarnbjo My friends who cycled from France to Mongolia said the stretch through Turkey was the worst, traffic wise — but that may have more to do with their route along a winding road along the north coast (vs. desolate off-roads in Central Asia) than with driver attitude. – gerrit Jun 06 '19 at 07:55
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    In the French Alps last summer, that "cold, moist...climate" was a blessed reflief from the heat (no long tunnels, but plenty of short ones). – Chris H - UK Jun 06 '19 at 12:33
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    @gerrit I cycled across the north Cape tunnel back in 2000. Still one of the most frightening experiences that I've had on a bicycle. Safe is really not a word that I associate with it. – Some wandering yeti Jun 06 '19 at 20:35
  • @Somewanderingyeti It wasn't particularly enjoyable, but when I rode it there were exactly seven cars overtaking me and I could hear each of them a minute before they came. Certainly a memorable experience. – gerrit Jun 12 '19 at 07:31
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Not the longest, but the 9 km long Oosterscheldekering is certainly noteworthy. Location of the Dutch Headwind Cycling Championships. This is the longest storm surge barrier and flood barrier in the world. There's a road and a seperate cyclepath crossing it. It consists of 65 pillars of 30 to 40 meters tall, with 62 sluice-gates of 40 meters wide and 6 to 12 meters tall over 3000 meters. It is also a hydro power plant. This is listed as one of the seven wonders of the modern world by the American Society of Civil Engineers, along with the likes of the Golden Gate Bridge and the Panama Canal.

While you're there, you'd also have the opportunity to cycle on/in:

  • The 5 km (3.1 mi) long Zeelandbrug, which was the longest bridge in Europe from 1965 to 1972.
  • The the 6.6 km (4.1 mi) long Westerscheldetunnel in the Netherlands. While usually only cars are permitted to drive through it, a few days a year it is open for cycle tours. The next one going through is the ZLM Tour on the 20th of June 2019.
  • The 10.5 km (6.5 mi) long Oesterdam. Part of the Delta Works, just like the Oosterscheldekering. This is a landbrige. Similar to the Afsluitdijk mentioned in gerrit's answer.
Belle
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The Chesapeake Bay Bridge Tunnel is 17.6 miles (28.3 km). It's not normally open to bicycle traffic (though shuttle busses are available to take cyclists and their cycles), but at least twice in its history, one span of the bridge has been opened for special cycling events (with cars redirected/restricted to the other span). If this qualifies, it's almost certainly the longest.

gerrit
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R.. GitHub STOP HELPING ICE
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Another "bonus" answer, longest elevated bike path 7.6 km (can be considered a bridge in some sense?). In the city of Xiamen, China.

https://youtu.be/hUbQyNLkjvo

Viktor Mellgren
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    That's really cool, I think I'd consider that within the scope of the question because it's man-made, not a ground level road, and it's made for cyclists so it's not a "special event" answer. So I'd cal this an actual answer, not a bonus one! – Bamboo Jun 11 '19 at 04:26
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The longest bridge one has already been covered, but the Hiawatha trail in northern Idaho features the St. Paul Pass Tunnel which is 1.661 miles (2.673km) long and it's designated specifically for bicycles. https://www.ridethehiawatha.com/the-trail

Eric J
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Additional bonus answer:

In Germany there is a mine "Erlebnis Bergwerk Merkers" 800m in the underground, which performs regularly bicycle events.

For example on 31.03.2019 there drove 50 cyclists 15km from "Schacht III" (lifting hole 3) to the "Kristallgrotte" (crystal grotto) and back.

Some tours are only cycling, others have stations where you could learn about the mine.

(Cycling tours in German language)

(Mine Merkers in general in English language)

Allerleirauh
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The longest tunnel open to cyclists in Japan is the Kanpu Tunnel (not far from the Route 317 tunnel listed in the question) and is 5,432m long. It has a reasonable gradient and took me the best part of 45 minutes to get through on my loaded touring bike. I rode through in the early morning and it was pretty much empty of traffic so it is definitely safe (especially if one goes the downhill way).

Japanese drivers are very courteous to cyclists (even if they pass a bit closer that you might be used to) and there are many tunnels that are many kilometers long that cyclists can get through safely.

paullb
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