Traffic Comes To A Halt When The Volume Of Traffic Reaches A Critical Value
Here is a article that describes a traffic model that has been developed that explains what I, and I'm sure many other drivers along crowded interstate highways have noticed many times.
Here is the LINK
I recall some years ago explaining to my kids as we travelled Interstate highway 85 in North Carolina that when the 'carrying-capacity' of a highway reaches a certain critical value a car could just tap it's breaks and cause a backward traveling wave in the traffic that would result in all traffic coming to a halt some miles behind the offending car.
I noticed this phenomena many times when returning home along I85 in North Carolina just after passing Greensboro NC heading toward Raleigh.
You could 'feel' the traffic load on the highway and you would know that there was no accident ahead but just the overloading of traffic.
Now this highway has been expanded to 4-6 lanes in each direction and this event rarely happens.
The solution to this problem is to equip all cars with GPS and proximity sensors and to equip highways with traffic volume sensors that would relay that information to onboard computers in cars to allow them to drive 'smartly' so the highway would not become so crowded. On a holiday weekend it would be the case that you would need to 'reserve' a space in the traffic flow for a certain time. You would not actually do this but your on-board computer would do it for you.