This sequence of eight quarter-mile timings is thought to start at milepost 173, the first after the tunnel, with the maximum speed at milepost 171.
I-17 has the unusual distinction of starting at approximately milepost 194 instead of at milepost zero.
In the 1770s, marble mileposts were installed along the way; many have survived to this day.
Other than a milepost, all the listed buildings are houses and associated structures, all but one dated before 1800.
However, his milepost timings are consistent with a speed of 100 mph or just over.
The trail is marked with mileposts, and starts in the vicinity of the visitors parking area.
This results in an unusual situation where mileposts overlap.
They match the mileposts along the road; it is thus easy to calculate how far one has to go.
