I agree with 2gypsies regarding big rigs going the opposite direction from you. What I noticed was when I lowed and moved right was that the big rig would do the same. Alaska Troopers are pretty tight when it comes to cracked or broken windshield. They write them up. A newer tractor windshield costs as much any two piece bus windshield and those truckers can't afford to replace them very often. I drove TOTW on a rainy day and once was enough. I'd stay a day or two in Dawson City and explore.
About slowing down, do it on the first day. There is so much to see that wasn't there or you were too busy dodging potholes to see 30 years ago and the difference between 35 to 55 and 45 to 65 is just and a couple of hours or so, one end to the other on the Alcan(it was the Alcan when I read my first copy of "Alaskan Hunter" back in 1949 and it still is as far as the DW and I are concerned.