I know friends in Alaska who are all too familiar with a very similar sensation. You’re driving outside town on some dark winter night when suddenly you can’t see the road. You begin wondering if one or both of your headlights burned out.

Then you realize that, most likely, the lamps simply got dirty, probably from all the road-sand kicked up by passing cars. So you pull over, grab a handful of clean snow in your glove, rub the lamps clean, polish them with a paper towel, get back in your car and continue on your way. Problem solved.

That thought occurred to me in the dark heart of Zion National Park in southern Utah yesterday less than a minute after entering the historic mile-long Mount Carmel Tunnel — one of the longest, narrowest and certainly darkest tunnels in America. The nearly century-old burrow passes through a sandstone mountain, inside of which there are no electric lights and no turn-outs and only one rule: DO NOT STOP.

For me and Harley, a better rule might have been: DO NOT ENTER.

For one thing, I had no idea how dark the tunnel was, nor how dirty (from a week of desert riding) Harley’s headlamp had become. For safety purposes, I hadn’t been riding at night at all, and this was the middle of the day.

Secondly, I didn’t know that in the very recent past — perhaps just five minutes earlier when I pulled onto the gravel shoulder of the park road to photograph the Bighorn ram on the cliffside — a small stone freakishly wedged itself between two teeth in my bike’s drive sprocket. And from then on, with every rotation, the little stone began sawing away at Harley’s thick, nylon-rubber drive belt.

So you can see where this is going.

But I didn’t. At least not then.

Entering the tunnel, I simply grew increasingly amazed at how dark and narrow it was. I checked my lights, but of course they’re automatically always on. So I switched on the bright light, but it was hardly better. I slowed down a bit. For some reason, there were no cars behind me to help illuminate the way, and the bleak way forward looked dark as a closet.

With two exceptions.

Every quarter mile or so, there was an opening on the righthand side of the tunnel where sunlight hitting the sheer cliff outside briefly shot through. For a moment I would get my bearings. Then it would be dark again. Also, two or three times, a car came straight at me from the opposite direction. For an adrenaline-inducing instant, its bright lights would both blind me and illuminate the narrow wormhole-like circumference of the tunnel — then thankfully pass on by. Then it was dark again.

So, yeah, I might have been looking forward to the end of the tunnel. Trying to make a little light of it, I might have thought to myself: Boy, what a lousy place this would be to break down …

When suddenly there was a great explosion from below … followed immediately by a loud FLAP-FLAP-flap-flap-flap! … followed by a total loss of power. Then kind of miraculously in the very same instant, the end was in sight. And Harley and I nearly coasted into the daylight, then I was able to quickly ground-pedal us all the way out of the tunnel and over to the side of the road.

In less than five minutes, a park ranger walked up to ask why I’d decided to park my motorcycle in such a precarious place. And I thought: not nearly as precarious as the inside of your tunnel.

But I was lucky he was there, because AT&T and my cellphone were both signaling “No Service” and I was fairly sure the nearest Harley Davidson shop was about 70 miles away. The ranger, however, had short-wave radio and was happy to call for a tow-truck. Which arrived about an hour and a half later.

So that’s why Harley and I are both residing for a couple of days in St. George, Utah, awaiting the special delivery of a brand-new drive belt. And grateful, too, for all our good fortune. Because, you know — it could have been worse.

I’ve also had a chance to piece together a short slideshow (see below) of some of the places and images from the week just past — as we traveled from Portland to Boise to southern Utah and ventured inside four national parks.

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