What does the term 'brake lag' refer to?

The term 'brake lag' specifically refers to the delay between the moment the driver applies the brakes and the time when the brakes actually begin to engage and slow down the vehicle. This delay occurs due to several factors, including the time it takes for the air pressure in the brake lines to build up and activate the braking mechanism. In air brake systems, the air pressure must travel through the lines and push against various components to engage the brakes effectively. Understanding brake lag is vital for safe vehicle operation because it affects stopping distance and overall response time in emergency situations.

The other choices refer to different aspects of braking systems: the cooling of brakes is not related to how quickly they engage, the distance traveled after brakes are applied is related to stopping distance, which involves both brake lag and vehicle speed, and the strength of the braking force is concerned with the efficiency of the braking system rather than the time delay in engagement.