I know it's a good 12+ hours after your shift would have started, but.....
Personally I believe you are the best person to judge what action you should take.
Unless I missed it, but the op hasn't said what the 8 mile walk in entails in terms of pavement conditions? If it's a nice straight road with grit and no ice on it that's one thing, IF it's anything like me (SE London) then I don't fancy your chances.
I live about 0.5 mile from the tube station and my walk back from it took at least double the normal time as my council are useless in gritting. Entire walk home was one big skate.
I slipped on the way back, cut my hand open on a fence and badly smacked my knee. So much so it hurts a lot to even walk.
Now, I mention this not for the overwhelming support and sympathy of you guys (

) but to point out if I did that in 0.5 mile walk (and I'm in good health), 8 miles in (assuming) similar conditions would be treacherous.
I will myself be going to work tomorrow even if it involves a lengthy walk. I know already a number of my colleagues won't make it in and will instead work from home. Am I annoyed by this? Only at the weather, not them. I'd rather them be at home for a day or two than break something on the way and be off for weeks.
Just my two cents though....