While on road trips I notice sometimes there are places where a road will deviate from the path I expect it to take. I take a note of it and then investigate what happened there. Usually there's some geography or history involved. Take I-5 in Northern California for example. There's a straight segment from Dunnigan CA to Williams CA:
But let's zoom in a bit, to Arbuckle CA:
I-5 looks like it'd be a straight line, but it bends to the west of town and then goes back to its original line. What's going on?
Interstate freeway I-5 from the 1970s mostly follows California highway CA-99W, which used to be US highway US-99 in the 1920s, which used to be Pacific Highway in the 1910s. That highway followed the Southern Pacific rail line, which used to be the Central Pacific Railroad's line in the late 1800s. And before that, there was the Siskiyou Trail from the early 1800s.
Why "mostly follows"? It's because CA-99 is still there, as is the rail line. The downtown commercial area of Arbuckle is adjacent to the rail line. The town was created in 1875 and the train depot was built in 1876. The commercial buildings were built near the train depot. A century later, when I-5 was built, they moved it several blocks to the west.
Arbuckle isn't the only place like this. Take a look at Williams CA:
Here, I-5 follows a straight line adjacent to CA-99W and the railroad, but then takes a detour to the east. The town of Williams also started because of the railroad, back in the 1870s. The freeway goes around the commercial district that would've started adjacent to the railroad.
You can see something similar in other towns along I-5 but it's not as obvious for some of the towns. It's really fun to look at historical maps to see how the towns have grown over time.
But it's not always a town that causes the deviation. Sometimes it's just an exit, as the overpass won't allow exiting onto the frontage road:
Why follow the railroad at all? My guess is that back when the US government was trying to encourage a transcontinental east-west railroad, they gave the railroads 200ft land adjacent to the track. That space would've been something the government could later use to build the freeways.
Labels: transportation
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