Yes, they were two lane roads. But no, they did not have impassable grades. Neither Loveland nor Berthoud Pass were easy, especially in winter, but they did in fact carry lots of commercial traffic (though I would think twice about sending an oversized load over them). In fact, to this day the old two-lane road of US 6 over Loveland Pass is used to keep hazardous material out of the I-70 tunnels.
I mean, I remember around 1968-69, before they finished building Interstate 80 up Echo Canyon, and that tiny two-lane road had to take all the commercial traffic that there was on "the main street of North America".
I mean, I remember around 1968-69, before they finished building Interstate 80 up Echo Canyon, and that tiny two-lane road had to take all the commercial traffic that there was on "the main street of North America".