Use Rebalanced Industries mod to reduce number of outdoor workers in industry areas.

Use Hide It or Remove All Animals mods to despawn animals (which count towards citizen limit).

If you have a decent computer, you could try More Vehicles Mod which increases the vehicle limit.

Certain ] increase or decrease traffic.

Use Crazy Tourist Fix mod prevent tourists getting stuck in your city.

Don't go crazy - AIs get confused if the capacity is too big (see: ]).

Use Advanced Vehicle Options to increase capacity of vehicles.

Use Optimised Outside Connections mod to ensure cargo vehicles are more fully filled with cargo.

Use Rebalanced Industries mod to reduce amount of industry traffic, especially in farms and forestry areas.

This will eradicate any 'stuck vehicles'.

TM:PE users: Use the ] tool, and also the Despawn.

Note: Don't use Show Limits or Show More Limits mods they are older and do not list all game limits. In particular, the vehicle and citizen limits can stop vehicles spawning. Then, in-game, click the limits button to show all the game limits. Install the Watch It mod, enable the limits display in its settings.

Still not working? Check vehicle and citizen limits:

Likewise, check any ] - do they have 'green time' for the required route?.

Check your ] and ] - can vehicles reach their destinations? ( example).

A route that's too slow or incurs too many restriction penalties will prevent routing.

If that fixed it, your ] and/or ] are the problem.

In ] settings, disable Ban private cars and trucks on bus lanes.

Read mod description page to learn how to use it.

Subscribe and enable Broken Nodes Detector.

Solutions Make sure there are no broken nodes

Vehicle limit (16384 maximum) reached - this can also be due to 'stuck vehicles'.

Vehicle management mods doing strange things.

There are many possible causes for this, including:

Industry trucks not spawning (first casualty of hitting the vehicle limit!).

Buildings spawn only a few vehicles, but never reach their full capacity.

One or more buildings never spawn vehicles.

Vehicles spawn, but quickly disappear (despawn).

Vehicle count on building info panel flickers between 0 and 1.

Outside traffic not spawning at highway outside connections.

Cities skylines mods not showing up