Transportation and Vehicle Safety: Emergency Brakes in Automobiles.

Question
Dear Michael

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/emergency-brakes.htm

1. Is Emergency Brakes Feature available in all automobiles ?. viz a. two wheeler scooters, motorcycles, bikes etc b. three wheeler viz autorickshaw, tempo c.four wheelers viz Cars, Jeeps, Trucks, Buses, Lorries etc ?.

2. In a rare case technically, the Emergency Brakes can also fail or not work in a automobile for the driver ?.

3. What are the real life situations where emergency brakes can be applied by automobile driver ?.

Thanks & Regards,
Prashant S Akerkar

Answer
Hi,

Thanks for asking.  My experience is limited mostly to four-wheel, non-commercial passenger vehicles, so I can't address your first question.  What I can say is that I had a lot of bicycles as a kid, and don't remember an emergency brake on any of them.  

Let me address your last question first.  The emergency brake (or parking brake) is a holdover from the days of manual transmission vehicles.  It's a mechanical component, a cable that runs from the handle to a single rear wheel.  It's purpose is to lock up that single wheel.  When a manual transmission vehicle is "parked", the driver typically places the car in either first gear or reverse, depending on the influence of gravity.  The parking brake then locks up a wheel to prevent the car from moving out of place.  In cars with an automatic transmission, the gear selection "Park" essentially locks the transmission and prevents the car from moving, making the parking brake redundant.  You may find drivers who have experience with manual transmission cars using the parking brake even with automatic transmissions.  It's habit, but it isn't really necessary.  Personally, I do it every time I park the car - one can never be too careful.

Beyond parking, another real-life situation that commonly utilizes the parking brake is in performance driving.  Using the emergency brake to lock up a single tire while throwing the steering wheel hard can cause the rear to break loose, inducing either an oversteer skid which can be controlled for drifting or a 180 degree direction change.  These maneuvers should only be performed in controlled settings by professionals.  It is not recommended to use the emergency brake for emergency braking, as it can cause the vehicle to slide out of control.  Rely instead on the car's main brakes.

The parking brake is traditionally a mechanical part, so of course it can fail.  If it does, it should be repaired as soon as possible by a qualified mechanic.  In some new cars, the mechanical brake has been replaced by an electric brake, activated by a button switch.  These, too, can fail, or may not work if the vehicle's battery has died.

Hope this helps!

Mike