Tmpe: Docs: Unprotected turns

[aubergine10]

Specifically, this: https://tmpe.viathinksoft.com/wiki/index.php?title=Vehicles_follow_priority_rules_at_junctions_with_timed_traffic_lights

Does that interact / overlap with the recent "turn on red" feature? Or does it only apply when the lights are on green?

Are "unprotected turns" and "turn on red" both affecting the same direction of turn? Or are they referring to opposite directions? (eg. one is about turning right the other about turning left?)

Also, why are unprotected turns only applicable to timed traffic lights?

[krzychu124]

Interesting and good question... Give me a minute I will try to check that

[krzychu124]

Here is what I've found.
If vehicle has priority it will use "unprotected turns" (vehicle won't stop) otherwise "turn on red" logic comes to play (vehicle will stop then leave junction if conditions are met)

[aubergine10]

Hmmm. This sounds strange to me. I will do some research to see what I can find, but I suspect that we might need to do further tweaks to the junction / lights logic.

[aubergine10]

This comment assumes vehicles are driving on the right (like USA and most of Europe).
For driving on the left, horizontally flip the line art below (segment C on the right).

Please correct me if I'm wrong, as the docs will need to clarify this with diagrams (time-consuming to produce). Also the mod will need updating accordingly.

Protected turn

The light goes green, and you can drive in the direction that light represents without fear of something crashing in to you. "You are protected"

Unprotected turn

The filter light (left or right as applicable to which side of road vehicles drive on) goes green, but you still need caution because there's other traffic that can drive across your path. "You are not protected".

      B
      |
C ----+
      |
      A

Cars at A want to turn left in to C, when the lights are on GREEN.

This means they will be driving across the path of cars travelling from B to A.

The unprotected turn is from A to C, as it cuts across oncoming traffic.

Turn on red

The light is red, but you can turn on red. (Note: A filter light would mean you can't turn on red, you have to wait for the filter to go green, or whatever).

      B
      |
C ----+----D
      |
      A

Cars at A want to turn right in to D, when the lights are on RED.

At a red light, they can do this if "turn on red" is enabled.

Priority signs

I believe (when applicable option selected) priority signs should affect both unprotected turns and also turn on red. The signs should affect normal junctions, junctions with normal traffic lights, and junctions with timed traffic lights.

• Stop: Cars must come to halt, check traffic, and make the turn when safe to do so
• Yield: Cars must yield to traffic, but otherwise can make the turn without stopping
• Priority: Cars can make the turn without stopping or yielding because they have right of way

If traffic is flowing from two segments of the same priority, the priority is determined as follows:

• Protected > Turn on red > Unprotected

Stop/Yield position

If Enter blocked junctions is enabled cars can part enter junction, like this vid, before stopping/yielding, when making an unprotected turn.

[krzychu124]

Looks good to me, very good.
That will be our goal for sure.
Some of these features were not made yet but we will try to implement them 😉

[aubergine10]

I've just made a few more tweaks to text above. It will need a few people to check over to make sure what's written there is valid for different countries. In particular stuff about filter lights (ie. specific left/right turn lights).

[aubergine10]

More precisely, an "unprotected turn" is any turn that has a risk of collision with other traffic. In that respect, "turn on red" is unprotected, depending on the traffic light sequence.

From this pdf:

• LTAP/OD: Left turn across path/opposite direction
• LTAP/LD: Left turn across path/lateral direction
• LTIP: Left turn into path
• RTIP: Right turn into path
• SCP: Straight crossing paths

So what we'd need is that conflict point detection, to work out when a turn would be unprotected.

When unprotected the priority system kicks in to decide who stops/yields.