Simulation error Object reference not set

Article verified: June 2019

Symptom

Both of these must be true:

• While loading a savegame, an error message appears:
  • Simulation error: Object reference not set
• On reviewing your log file, the stack trace mentions:
  • RoadBaseAI.CanEnableTrafficLights

Some other error? Try: Object reference not set to an instance of an object

Cause

This is a bug in the game itself, not TM:PE.

This problem occurs when your savegame includes a road asset which is no longer available, usually a result of one of the following:

• You unsubscribed a road asset
• You unsubscribed a mod that provided the road asset (such as Network Extensions)
• The author of a road asset (or mod that provided one) deletes their workshop item, which also removes it from your game

Solution

• Quick fix: Subscribe and enable Safenets mod
• Otherwise, see: How to remove workshop networks

Fixed?

If not, it's likely your save game is lost, sorry.

Something else? See: Troubleshooting