Two athletes are going to run/bike a distance. There is one bike, which will be exchanged between athletes. Normally the biker stays next to the runner.
This simulation is targeted at the athletes who want to run more instead of biking.
Example: when you run 12kmH (5min/km) and bike 20kmH (3min/km) you'll take 8min for 2km, that is 15kmH (4min/km).
The only difference:

• You go faster
• Don't have your water, food all the time (assuming it's on the bike)
• The biking part becomes harder
• Need to have two keys and a quick release lock
• You can't communicate about your progress/speed
• A bicycle computer is needed

When biking and running, the two athletes constant switch bike.
This simulation shows how this will take place. It is important to look for an alternating pattern in which there is no overlap, since it isn't possible for two people to bike at the same time.
One athlete cycles the bike in front of the other, leaves it there and starts running. The other athlete jumps on the bike and bikes until the agreed switching distance.

If the biker is at the switching distance but hasn't passed the runner, the biker needs to bike further until he has passed the runner and place the bike a couple of meters ahead of him (you can exchange keys while passing since you only leave the bike for a couple of sec unattended). When the biker needs to bike further it means that the runner was faster (biking and running). But this results in the biker needing to bike more, and the runner needing to run more. This will even out the difference. (assuming that biking is easier than running)

Example: You have agreed on switching at every KM, the person on the bike cycles until the next whole KM is reached on the bike computer. If he needs to bike further, e.g. 1.5km instead of 1km, he bikes further and the runner will only do .5km until the next whole km.
By doing this, the system will even out automatically.