Looking at a variety of maps, it seems that even in the flat states like North Dakota, Kansas, Nebraska, etc. even the straightest of roads has a bit of a jog in it after 30 or 40 miles, going off the straight and narrow a bit to avoid a gully, knob, wash, or uncommonly large anthill.
Can anyone point me to the longest continuously straight road in the US? How about the world? I suspect Australia ought to be good for some unveering distances.
LMGTFY
North Dakota Highway 46, is supposedly the straightest of them all – plumb line straight – the longest straight road in America. It stretches across 123 miles of north Dakota prairie from Hwy 30 in the west to a nameless county blacktop just past I-29 in the east, a steady 20 miles south of I-94.
someone else can do the world
What about the curve by Little Yellowstone Park?
Yeah, but if you read more closely about that road, you get this: “its longest straight-as-an-arrow, lock your steering wheel and take a nap stretch – extends nearly 31 miles, from Gackle to Beaver Creek.”
So I don’t buy it as the record at 123 miles.
You didn’t think it’d be that easy, did you?
That’s snark. “Let me Google that for you”.
Googling led me to incomplete, if not wrong answers. So I asked here.
The longest straight stretch of road in Australia is claimed to be on the Eyre Highway across the Nullarbor Plain, at 91 miles/147 km. I’ve taken a bus across it, and it’s pretty dam straight.
The Nullarbor has the longest straight stretch of railroad in the world, 297 miles/478 km.
I assume Lombard Street is out of the running.
OK, the results so far:
World record 91 miles, Eyre highway, Australia
US record 35 miles, US-80 in Utah, Bonneville Salt flats.
Googlemaps confirms this.
Confirms which? The 31 miles or the 123 mile claim?
Lotsa wobbles on hiway 46 in ND, one at Gackle, one at county road 63, one at Little Yellowstone park.
Still, I get a stretch that’s pretty straight from just south of Kindred to Little Yellowstone park that is about 43 miles.
US 136 across central Illinois?
Due to the curvature of the Earth, would a tunnel like the Chunnel be a better pick? 
Hm, 86 miles straight from west of Rantoul to just a few miles east of Havana!!
We have a new contender for longest US straight road, it seems.
Thanks!
Highway 85 across norther Saudi Arabia gets my vote… looks like well over 100 miles totally straight.
Just a thought but how are you defining straight? At what point does the curvature of the Earth become relevant? Consider a road 1 km from the South Pole that heads due East… 
Or better yet, the path Eärendil sailed.
It sure isn’t anywhere near San Francisco.
I’m sorry. I couldn’t resist a twofer.
Not really. Look where it encounters Interstates 74, 55 and 155: in each one of those, 136 splits out a suicide or left turn lane, causing the primary lane to deviate from plumb. Looks like those segments are too short together to merit any kind of record.
I was going to lobby for some 40-odd miles of Hwy 17 north of Alamosa Colorado just past the road to Sand Dunes NP, but it looks like the road has a very subtle wander to it.