A test of a driver\'s reaction time is being conducted on a level testing track

Question

A test of a driver's reaction time is being conducted on a level testing track with wet pavement, satisfying the general conditions applied for road designs. The initial driving speed of the test car is 90km/hr. When the driver is sober, a stop can be made just in time to avoid hitting an object that is first visible 160m ahead. After a few drinks under exactly the same conditions, the driver fails to stop in time and strikes the object at a speed of 55km/hr. What is the difference in driver reaction time before and after drinking? (Use Austroads Guide equation presented below and round answer to 2 decimal places) RTV v2 SSD-3.6 254+0.016) Answer:

Explanation / Answer

In the given equation

SSD= stopping distance (m)

d = coefficient of longitudinal deceleration

Rt = driver reaction time (sec)

V= initial speed of Vehicle (km/hr)

a= longitudinal grade (+ve uphill and -ve downhill)

Here initial speed V = 90km/hr

SSD = 160m

speed after drunk driver applied brake 55km/hr

since the test is being conducted in level track G =0

let us assume coefficient of longitudinal deceleration (d) as 0.4

Before drinking

160= (Rt*90)/3.6 + (90^2)/(254*.4)

therefore, Rt =3.21 sec

After Drinking

160 = (Rt*90)/3.6 + (55^2)/(254*04)

therefore, Rt= 5.21 sec

The difference in driver reaction time before and after drinking is 2 sec.

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