[mloveland78]

The "target" speed of 45 mph is there for points which count towards the overall score for the day. The points from the morning and afternoon events are combined for the overall score with equal weight given to points from each. However you can only earn 30 points in the morning event, and I'm not sure how many points can be earned in the rally event but it is a lot more. The overall winners are those who do well in the rally.
The "target speed" is measured by your lap time which I and Bricepick have posted about before.
If you just want to have fun and / or maximize fuel economy you can do any speed between 35 and 65 although they do not sit there with a radar gun aimed at you the whole time. As long as you are not endangering yourself or others you are OK. We are encouraged to follow the rules of the road while on the track and use turn signals when changing track positions and be cautious of other drivers.
With that said there are always a couple of people who are there in high performance vehicles who are just having fun going round the track. Our Green Grand Prix event is significantly cheaper for the amount of lap time that we get than what people normally have to pay. Some are smart enough to take advantage of this on opening weekend to get some cheap track time. We have had a Toyota Supra and a Jeep Cherokee SRT8 on the track with us before and they were lapping everyone and driving fast but safe.