All due credit for the article today goes to a reader using the pseudonym "Wangi." He sent me an email message offline noting an interesting situation, which by implication suggested the basis for another contest. I even stole the title of the current article from him. Thank you, Wangi!
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There’s nothing unusual going on here, right? This is a one mile (1.6 kilometre) stretch of motorway outside of Edinburgh, Scotland. Open that map in another tab though, reverse the directions (the little button with the up and down arrows next to the origin and destination information) and notice the result. A simple 1.0 mile trip from Point A to Point B becomes a 16.3 miles (26.2 km) odyssey when returning from Point B back to Point A. The lesson to be learned with this simple exercise: a motorist taking the wrong exit near Edinburgh will have a bad day.
Wangi wanted to know, "what’s the longest round trip for what should be a straightforward 1 mile?" I’ll take my shot at a roundabout answer and then turn the same question over to the 12MC audience playing at home. The key, I think, is embedded within the design of limited access highways. Find a roadway with the longest distance between exits and one stands a pretty good chance of solving the puzzle. There might be other situations causing lengthy reverse trips and I’ll get to some of those momentarily. I’ll concentrate on limited access highways first.
U.S. Interstate Highways
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I’ll stick with what I know and examine the Interstate highway system in the United States. That leaves the rest of the planet to 12MC readers worldwide to scour for better examples. I had a hazy recollection of the longest distance between exits somewhere in western Utah, an interesting situation brought to my attention by a reader after my drive through the Bonneville Salt Flats a couple of years ago. I also noted that I’d experienced a similar situation when I drove across the Lake Pontchartrain Causeway in Louisiana. Get on either of those roadways and it’s going to be a long time before one will be able to loop back to the start.
Notice the Bonneville example, above. This solution leverages a 37 mile (59.4 km) gap on Interstate 80 between Exit 41 at Knolls and Exit 4 at Bonneville Speedway. It’s one mile heading east-to-west and then 74.1 miles (119 km) to return to the original starting point. A fictional trip taking 48 seconds in one direction will take about 1 hour and 4 minutes when reversing Google Maps’ directions.
A one-mile Lake Pontchartrain Causeway trip, by the way, would take 47.9 miles (77.1 km) when reversed. That’s a healthy distance (map) although it falls well short of Bonneville. It’s also not an Interstate highway segment, which leads to the next slice to be considered.
U.S. Limited Access (Non-Interstate) Highways
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Florida’s Turnpike includes an insanely long segment without exits between St. Cloud and Yeehaw Junction, formerly known as Jackass Junction. The 48.9 mile gap is reputed to be the longest in the United States of any road. Miss that exit and one will feel like a Jackass because reversing a one mile trip will take 104 miles (167 km) as Google Maps displays it.
In reality, the Canoe Creek Service Plaza (map) sits between the lanes and caters to traffic heading in either direction. One could flip sides there safely. No physical barrier seems to prevent it. It’s still going to be a humongous detour, just not as bad as it may appear at first glance. Nonetheless, Google Maps does not recognize it as an option which leads me to wonder if it’s legal. Toll roads sometimes have odd rules. Does anyone have first-hand experience with Florida’s Turnpike and know the answer?
Other Possibilities Worth Exploring
My stop at the Alpine Visitor Center several years ago
What’s the longest reverse direction that doesn’t involve a limited access highway? I’ve already mentioned an example that involved a bridge, and there may be longer ones. Another possibility might be one-way scenic loops. There are several in the National Park system. I’m personally familiar with Old Fall River Road in Rocky Mountain National Park (my visit). It’s limited to uphill traffic because it’s narrow, gravel and full of switchbacks. Eventually it arrives at the Alpine Visitor Center at an elevation of 11,796 feet (3,594 metres) and connects there with the Trail Ridge Road. Google seems to think Old Fall River Road allows two-way traffic (map) — it does not — so I can’t calculate the the exact reverse distance easily. I’d estimate it to be about 25 miles give-or-take.
I’d be curious to find the most extreme distance reversal differences in a urban setting. The one-way roads that users offered in Just Keep Turning offered some interesting possibilities. Reader "Pfly" highlighted a good example in Rome with a fairly significant percentage difference when reversed (map).
I think this should be examined in categories: biggest differences for limited access motorways; for bridges; for loop roads; for urban environments and whatever else seems meaningful. It’s not fair to compare Florida’s Turnpike to Rome.