Bicycle Brake Reaction Time means the time a cyclist needs to -

see a danger ahead;

perceive what it means;

decide on a response; and

instigate that response,

when the bicycle continues to travel at is velocity.

A cyclist who is concentrating will have a Bicycle Brake Reaction Time of about 2 seconds to react to 'instigate a response' by squeezing his/her brake levers according to different, previously determined, pressure levels for the front and rear brakes when in an emergency situation.

A Brake Reaction Time of 2 seconds, which has been used in the below separate formulae for km/p/h and m/p/h on page 41 of  Guide for the development of bicycle facilities provided by the 'American Association of state highway and transportation officials' is the mode Bicycle Brake Reaction Time used in most modelling.