Chicago Transit Authority (CTA) Bus Practice Test

Buses operating within city borders are permitted to idle for a maximum of three minutes to build air pressure. This policy is in place to ensure that the air brake systems, which rely on compressed air, function properly before the bus begins moving. Allowing for this time is critical for safety, as adequately built air pressure ensures that brakes will respond effectively when needed.

This three-minute rule supports both operational efficiency and compliance with environmental regulations, which often aim to reduce unnecessary emissions from idling vehicles. Recognizing the importance of safety and environmental considerations, transit authorities have established this guideline as a standard practice for drivers.