I have about a 2' shoulder on a 55+ MPH road, it's the last 2.5 miles of my commute. Combined with the somewhat wide lane, it's plenty of room, but I don't know what the rest of your road looks like, other than the 1.5 foot shoulder.

A couple of months ago I decided to trump DST, so I started going in at 5AM, so I can leave at 2PM. That helps a lot; traffic at 5AM and 2PM are a lot less than at 8AM and 5PM.

The only time I'm pretty nervous is if there's enough snowfall to make the shoulder on that 2.5 miles unridable (it gets so greasy and rutted I can't ride it even with studded tires). Last year that put me out of business. However, this year I found an alternate route; it does add 2 miles of gravel road to my commute, but it takes the distance on the busy road down to just a few hundred feet. If I have to I'll walk that distance. So hopefully I'll stay in the saddle more this year.

I drove today. I had a cold, was going to blow off, decided I had too much work, so I drove. Shoulda ridden anyway; I would have felt a lot better during the day. This fall I've really become seriously polarized against driving; on days when I drive, I'm irritable and really don't feel very good. When I ride (which is all but 2 or 3 days a month) I feel great. It's amazing; even if I got too little sleep the night before, and I'm dragging ass at home, by the time I ride to work, I'm ready to go for the rest of the day.