I was driving home last night, and the HPS streetlighting all along the freeway was strobing, flashing on and off approx once per second.

I did not think it was possible for HPS to have such a quick restrike time

What could have caused this?

The Lucalox Superlife have no re-strike time, there are some other lamps made like this as well.
http://www.gepc.pl/lighting/do_pobrania/Lucalox%20-%20Ulotka%20(angielski).pdf

Also, on page 4 they have a short explaination of why they might be blink off and on, possibly due to wind or traffic vibration? Next guess would be strange voltage disturbance?

I once went to a seminar put on by a lighting manufacturer. The only thing that I remember about the context is the fact that if a HPS fixture cycles on and off, it is the bulb. Through the years, I have followed this rule, and have found it to always be true.

the restrike time is proportioinal to how hot the bulb is. if the bulb is not hot because it didnt light completely before the next power interuption it will restrike faster.

Some years back a shopping center had the same thing happening to an entire parking lot. They later found the cause when the circuit breaker caught fire. (It was arcing internally until it finally failed.)

So I would think that anything which causes an arc fault on the circuit would cause that effect. (Bad underground splice/feeder, etc.)

Arc faults would chop the current so fast that the bulb wouldn't go completely out, so it can strobe faster than the igniter would pulse it.

Were you a good samaritan and called the highway dept.?