What is one common indication that a vehicle may be a gross polluter?

One common indication that a vehicle may be a gross polluter is the production of excessive smoke from the exhaust. This visible smoke typically signifies that the engine is burning fuel inefficiently or that there are issues with the vehicle's emission control systems. Such conditions can lead to the release of harmful pollutants into the atmosphere, indicating that the vehicle is not complying with environmental standards.

Loud exhaust systems might suggest modifications or performance enhancements but do not directly correlate with excessive emissions. Tinted windows can affect visibility and driver safety but are unrelated to the vehicle's emissions performance. A broken air conditioning system, while potentially indicating maintenance issues, has no direct impact on the vehicle's emission levels. Therefore, excessive smoke is a clear and direct signal of a vehicle's potential to be categorized as a gross polluter.