In reply to Godwin:
Stuff like that already exists at least here in France. A few times I've signed up for a trail race and they have links for the car sharing. I've even offered a lift but never actually used it.
There's an app called BlaBlaCar which is a more up to date one bit again never used it. I think it's more for trying to cover your costs as a driver.
Where I live we have physical, official car sharing stops dotted about which are like bus stops but marked, and with a panel with buttons with the main destinations which you press along with how many people there are. Then when a car passes, it is automatically detected and the required lift details are flashed up so you can stop and offer if it works for you.
There's also an app for people who live in my area and regularly commute by car to Grenoble to be able to formally offer lifts. Again doesn't work for me so o can't remember the name.