As mentioned in another thread, traffic lights could be adapted to work better with custom lane routing at intersections.

On top of that, if we ever got priority lanes ('right of way' and 'give way'), those could buff traffic lights on those lanes - ie. give way gets less 'green time' and right of way gets more 'green time'. This would avoid cumbersom traffic light timings like in TM, yet still give a good result.

Sorry Sajiki, I haven't noticed this discussion before.
The discussion aubergine18 mentioned is this.
To answer your question, I have no plans to add timed traffic lights to this mod as I don't think they are a good thing in the long run.

Having spent several hours experimenting with the traffic lights in TM mod, I can safely say that if T++ ever does implement traffic light features, use a completely different approach to TM.

I was drawn in by TM's nice looking UI - the screenshots look great, but in practice it's a completely different matter. I struggled to get even the basic traffic light customisation working, yet alone the more complex timed traffic lights.

The way I'd approach timed traffic lights is as follows:

- Define a priority route (right of way / give way)
- Wait to see what effects it has on traffic
- If side roads are struggling to access the main route, add traffic lights
- Seeing that they are on priority route, traffic lights automatically adapt and synchronise

In other words, I'd have timed traffic lights be simply an 'extension' of priority lanes, for use in cases where side street traffic is struggling too much.

If you imagine the priority route like this, where - is the main route, < shows direction of the route, and + are traffic light intersections...

<--+---+----+---+

The light nearest the < end of the route would be the master, it would change first and then the others would change in seqence towards the other end of the route. The sequence you'd get (from traffic travelling along the main route) would be something like:

<--R---R----R---R
<--G---R----R---R
<--G---G----R---R
<--G---G----G---R
<--G---G----G---G

So traffic is leaving the route at the < end to make way for next light as it goes green, and then this sort of ripples along the route.

Obviously it's not that simple - junctions can be more complex, and there's also intersection routing customisations to take in to consideration, but you get the general idea.

As for non-timed traffic lights at an intersection, they could just automatically update when intersection route is customised, based on where the routes cross over each other. The sequnced (timed) traffic lights would really just be a synchronisation effect as described above.

Users wouldn't actually ever go in to edit traffic lights, the traffic lights would just sort themselves out based on intersection routing and priority lanes. Traffic lights that don't make things worse is what users want, not cumbersome/confusing UI to edit traffic lights.

What would be nice, in terms of UI, would be something like TM has in the visualisation of traffic light states - but not as an editing tool, more of an information overlay. So you could toggle the overly (via seprate button, similar to how one way street arrows mod works) and then just sit and watch your traffic lights change from above. Would be like the circles used for intersection routing, but they'd be filled and either red or green depending on the state of the traffic light for each lane. I could stare at that for hours, and it would be useful visualisation prior to customising routes at complex intersections.

All of that would be quite some challenge to implement, but if achievable would be a true sight to behold.