Atleast with the original Traffic Manager mod, this was caused when you saved your game in the cloud.

So avoid saving to cloud, it breaks traffic lights

No, i dont saving in cloud, i save normal on disc.

Another cause to the problem is if you bulldoze an intersection BEFORE you remove the timed trafficlights node. Same if you change the roadtypes over the intersection.

If you are doing changes to a road that passes thru a timed trafficlight intersection, then make sure you delete the node first.

If the damage is already made, you either load an earlier save, or reset your timed traffics lights by deleting the file that is created in conjunction with each savegame where the nodes and times are stored. That will remove all timed traffic lights though. :/

I noticed that this mod says it has fixed the negative timer bug:

http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=481786333

Maybe worth chekcing into?

This could be due to a bug that's been present since the early versions of the original Traffic Manager mod, I'll take a closer look soon. @Jackedup You may have missed the point of this mod, there are several added features! :)

Oh no, I certainly appreciate what your mod does, that's why I installed it. I juist found that similar mod and thought maybe his implementation of the fix could work for you as well.

Did you try to implement the solution for this negative count into the newest update?
I'm still having this issue...

@Jackedup Oh I see, then I'm the one who missed the point of your post! Thanks! :)

@MrPizzaCrust Unfortunately, I've never had this particular error myself and I thought it only happened when you tried to save to cloud. If you have an output_log with these errors, could you please post it on pastebin so I can take a look? Thanks!

Hi everybody! In my case negative count was happened because of "ARIS remove stuck vehicle". Swithing off this mod solved the problem.

same problem here! the timed traffic lights have no effect at all. i have follow several traffic mods, but this is the only one installed.

@Decay Do you get any errors in the output log? What do you mean by no effect? Remember you need to click on "Save" when defining new traffic light states.