There are 2 passengers and a driver in each car, which means that in each car there are 2 passengers + 1 driver = <<2+1=3>>3 people.
This means there are a total of 20 cars * 3 people per car = <<20*3=60>>60 people in the car at the start of the race.
At the halfway point, there is an additional 20 cars * 1 additional passenger = <<20*1=20>>20 more people.
So be the end of the race, there are 60 people at the start of the race + 20 additional people = <<60+20=80>>80 people in the cars.
#### 80