Remember - we all heal differently, and at different rates. Add to that the fact that we probably have very different work environments and it is all a big dice game. I was able to go back to work after about 5 weeks, but I went part-time. My doctor would only authorize my return to work part-time until 8 weeks after surgery, then he allowed work "as tolerated." By 9 or 10 weeks, I was back to my regular 10-hour days - but I work at an executive position in an office, with no business travel required.
I had no problems driving after 5 weeks, but I did have to be extra careful when backing into my driveway. The driveway is between two houses, and is about 120 feet long. You have to either back in or back out - no room to turn around. At the time I had a very large car, with full-power everything, so effort wasn't the issue. Twisting and turning my body was the limiting factor, but as long as I could go slowly I had no issues. Day-to-day driving, with power steering and automatic transmission was no problem. Some folks have expressed fear over what may happen if they had an accident, but my doc felt that for an accident to be truly threatening to a healing sternum after 5 weeks would have to be a life-threatening impact, and if so, the sternum might not be the biggest worry.