There's a 2km long tunnel on the route I tried last week. Since it's all downhill (the way I go, anyway) it's not too hard to stay near or above the 60 km/h speed limit through the whole thing. Still, as could be expected, a few cars passed me. There are no signs saying bikes aren't allowed. Is there any reason I shouldn't be doing this?

Is the tunnel lighted? Can you see straight through the tunnel?
If yes to those it should be ok, but if its real dark it can be dangerous with or without cars

Lighted or not, at least have some blinkies going off. Drivers entering from outside the sun, especially with sunglasses on might not even ****in see you.

If it gets your blood pumping, do it.

+1 for the light. I'd have a blinking red taillight at the least.

We have a mt. tunnel on one of our weekly rides. It is short, but it is dark and narrow... and the traffic is moving along a pretty brisk pace. Occasionally a truck driver will have the foresight to see what's happening, and will slow down enough to essentially run blocker for us. Passenger car drivers almost never get this and will try to squeeze by, no matter how narrow, even though it would only cost them about 3 seconds to wait for us to exit the other side.

Vance, which tunnel are you talking about? I have to say that Sepulveda is nice because they have that button that starts a flashing light telling drivers there is a bike in the tunnel. They should do the same on Kanan.

As a fellow rider in the Osaka area, I am very familiar with your problem. I try as hard as possible to avoid tunnels. Over the years, I've learned that the older roads that the tunnels have presumably replaced are usually still there. So in many cases, you probably have an option--if you don't mind the climb. Tell me what tunnel you're talking about. There's a chance I know it.

Use blinky, get in, get out, no messin about.

Dude, didn't you see the movie Heaven Can Wait??? Riding a bike through a tunnel was exactly how Joe Pendleton got killed. Actually, the angel took him away just before impact and it turns out he would not have been killed, but you get the idea. Tunnels are dangerous. Then again, maybe you can be brought back to life, put into the body of an NFL quarterback, win the Super Bowl, and date Julie Christie. There are worse fates in life.

A long time ago, a seasoned roady told me he went through a fairly long tunnel on the N.C. parkway, one that is curved such that at the ~midway~ point it was so dark he couldn't make out light at either end. He said it was the most scared he's ever been. (I assume he rode it at speed).
Before he took up riding, he was one of the boldest rock climbers around, among the first to solo whitesides mtn. in the 70s. It's ~1000' high so I imagine he had a good grasp of managing fear.

Are daytime headlights required in Japan? A relfective vest of some sort would help a lot in that case.

You can't see from one end of the tunnel to the other, but it is lit. Also turns out that the speed limit is 40 km/h, not 60.

Daytime headlights aren't required here, but most people put their lights on in a tunnel.

I tried it again today and remembered to bring my red blinkie. Good times ! Thanks for the advice.

Oh, hey, just noticed this! We ought to meet up for a ride sometime. It's the Mizu(somethingorother) Tunnel. I made a point to remember the name today, and promptly forgot it. It's on or near route 309 (or is it 27?) down by Tondabayashi and Nara-ken.

There's a tunnel running by LAX that specifically won't allow bicyclists. On my ride to San Diego, going down Sepulveda Blvd to connect to PCH (Pacific Coast Highway), I had to backtrack and take another route (Aviation Blvd) around the airport.

The tunnels I 've riden through, they were dark and creepy. One definitely needs some lights. It was maybe a km long. but, what i did not like besides the traffic, the shoulder was almost non existant and the road was covered with crap, that I could barely see.

The tunnel that runs in front of the United Nations under 1st Avenue for a few blocks is a blast if you time your entrance between traffic flows, and keep a pace of at least 27mph. The police have never bothered me about it. If they do, you can always say there were no signs telling you not to, and promise not to do it again.

Seedy J...I've sent you a private message...did you get it?

Just came on this thread. My rule of thumb for tunnels in Japan - if I've never been through the tunnel (in car or bike) and I can't see the other end of it AND it doesn't have a sidewalk I can ride on, I don't enter it.

There's inevitably going to be a road around the tunnel or over the tunnel that will be safer (though maybe steeper or a little more beat up).

I know I'm not Vance, but it's the Malibu canyon tunnel. I drive Kanan quite often and rarely see cyclists there. We seem to avoid it on the bikes probably because of the tunnels and traffic.