The overlap approach is imho too vague and too maybe a bit too restrictive as well as a tool to decide fault. Just because someone has the overlap momentarily does not mean he actually was in a position to pass. At what point is the overlap measured and how does once achieved overlap effect the rest of the turn? In spa rosberg had a lot of overlap going into the corner but did not have almost any of it at mid turn anymore. On corner exit he was basically behind hamilton apart from his front wing.
The thing is if you measure overlap from corner entry then late braking may automatically become dive bombing (despite being legal passing move otherwise) because at the initial braking point the cars are not side by side. If you measure overlap at mid turn then how do you deal with switchbacks? And if the overlap only matters in corner exits then it is a moot point anyways because if you are side by side on corner exit the move is basically done already. Unless you only want to prevent drivers pushing others off the road on corner entry. But that would be a good start. It is kinda crazy that on corner exits being fully alongside means the driver inside can still legally push you off the road (most of the time) but doing the same thing on corner entry is forbidden.
If we want to reduce the collisions I think this challenge based approach that I just invented could work little better (being my idea...:tilt. If the drivers are close enough so that they can not freely run any line they want then both of them need to leave room at all times. Basically if a position is being challenged you can not take a line that causes a collision if the other driver doesn't back off even if the other drive only has his front wing next to you. In a way this is a bit like the nascar rule where any overlap is sufficient (at least early in the race).
This rule would effectively prevent drivers from running other drivers off the track on corner exits. It would make it easier to solve situations where two cars hit each other on the straightaway for example. But the most important thing this kind of rule prevents is the drivers saying he did not see the other guy. I think seeing is way overvalued when it comes to passing and defending. It is not about seeing where the other guy is. It is about knowing where he is. And equally about not knowing. Sometimes not seeing is not knowing but most of the time it isn't.
This rule would not eliminate defending either because it doesn't really change the wording of what defending is. Defending doesn't allow you to drive into other people. So in a way this rule would have similar goal. To prevent contact. But if you are ahead you can still choose any line you want as long as you are not weaving all over the place.
And most importantly it could improve the racing. Going around the outside is very difficult nowadays in F1 because the rules most of the time allow the car on the inside to drive the other car off the road on corner exits. If driver were expected to leave space then that would be automatic penalty. Instead of looking for the overlap we simply look whether two drivers were racing for position or not and were they close enough.
With this rule here are few examples. First obviously the robsberg/haemitlon/spa. Clearly the position was challenged by robsberg when going into the corner. So haemitlon should have left space according to this rule. This is the interpretation based on this rule and not the rules that are in effect now in f1.
Then haemitlon/moneynada/valencia. Hamilton should have left room for maldonado on corner exit.
Vetlel/Kubic/Australia: https://www.youtube.com/watch?v=aPXVzLTPIxo
No penalty as vettel left room on the outside.
In this clip maldonado does nothing wrong:
https://www.youtube.com/watch?v=nw-HjaKxA4Y
Vettel gets a penalty:
https://www.youtube.com/watch?v=vx9zIQvrdZU
Massa gets penalty:
https://www.youtube.com/watch?v=B33HaWnDovU
Perez gets penalty:
https://www.youtube.com/watch?v=T1ap51Gu390
The thing is if you measure overlap from corner entry then late braking may automatically become dive bombing (despite being legal passing move otherwise) because at the initial braking point the cars are not side by side. If you measure overlap at mid turn then how do you deal with switchbacks? And if the overlap only matters in corner exits then it is a moot point anyways because if you are side by side on corner exit the move is basically done already. Unless you only want to prevent drivers pushing others off the road on corner entry. But that would be a good start. It is kinda crazy that on corner exits being fully alongside means the driver inside can still legally push you off the road (most of the time) but doing the same thing on corner entry is forbidden.
If we want to reduce the collisions I think this challenge based approach that I just invented could work little better (being my idea...:tilt. If the drivers are close enough so that they can not freely run any line they want then both of them need to leave room at all times. Basically if a position is being challenged you can not take a line that causes a collision if the other driver doesn't back off even if the other drive only has his front wing next to you. In a way this is a bit like the nascar rule where any overlap is sufficient (at least early in the race).
This rule would effectively prevent drivers from running other drivers off the track on corner exits. It would make it easier to solve situations where two cars hit each other on the straightaway for example. But the most important thing this kind of rule prevents is the drivers saying he did not see the other guy. I think seeing is way overvalued when it comes to passing and defending. It is not about seeing where the other guy is. It is about knowing where he is. And equally about not knowing. Sometimes not seeing is not knowing but most of the time it isn't.
This rule would not eliminate defending either because it doesn't really change the wording of what defending is. Defending doesn't allow you to drive into other people. So in a way this rule would have similar goal. To prevent contact. But if you are ahead you can still choose any line you want as long as you are not weaving all over the place.
And most importantly it could improve the racing. Going around the outside is very difficult nowadays in F1 because the rules most of the time allow the car on the inside to drive the other car off the road on corner exits. If driver were expected to leave space then that would be automatic penalty. Instead of looking for the overlap we simply look whether two drivers were racing for position or not and were they close enough.
With this rule here are few examples. First obviously the robsberg/haemitlon/spa. Clearly the position was challenged by robsberg when going into the corner. So haemitlon should have left space according to this rule. This is the interpretation based on this rule and not the rules that are in effect now in f1.
Then haemitlon/moneynada/valencia. Hamilton should have left room for maldonado on corner exit.
Vetlel/Kubic/Australia: https://www.youtube.com/watch?v=aPXVzLTPIxo
No penalty as vettel left room on the outside.
In this clip maldonado does nothing wrong:
https://www.youtube.com/watch?v=nw-HjaKxA4Y
Vettel gets a penalty:
https://www.youtube.com/watch?v=vx9zIQvrdZU
Massa gets penalty:
https://www.youtube.com/watch?v=B33HaWnDovU
Perez gets penalty:
https://www.youtube.com/watch?v=T1ap51Gu390