There is a fantastic safety tool for Streets and Trips that in my view is a step up from the standard GPS device. It's called 'The Spacebar'. Hitting the spacebar replays the last instruction immediately - and if you continue to press it, it continues to count down the distance to your turn - to the foot.
For safe operation - the key is that you have set your laptop up so that the volume is properly adjusted. If you have an MP3 jack in your newer car - great - connect right to it and play directions over the stereo. If not, and your laptop speakers are too weak - get a U.S. $15
external speaker (also need Mp3 cable) from Radio Shack , it'll knock you out of your seat.
Additionally - you simply have to set up your route before you start driving - you have to commit to that. There's allot of things that shouldn't be done driving: reading hand written directions, setting a stop in your PND, adjusting your stops in S&T , dialling a phone - etc.
Back to the space bar - so I don't have to take my eyes off the road - I place a piece of fuzzy velcro on the bar. That way - when I reach over, I know I'm on the spacebar without looking.
The spacebar is an extremely valuable safety tool. Give it a try!