Arrive Alive

Stopping Sight and Driver Reaction Time

Stopping Sight Distance

S=dr+db

S=stopping sight distance
dr=driver reaction distance (decision distance - combined observation, identification and decision distance)
db=braking distance (action distance)

dr=v.tr

db=(v*v)/(2g(f+-G))

v=speed
tr=driver reaction time (varies from 2,5 to 2,8sec)
g=acceleration of gravity
f=coefficient of friction between tyres and pavement (varies with speed – for wet, glazed asphalt it varies from about 0,45 at a speed of 10km/h to 0,2 at a speed of about 70km/h)
G=average grade

The above distances depend on whether a vehicle goes into a skid or not – distances increase drastically when vehicles go into a skid.


 

 

The type of vehicle (vehicle mass – together with speed relating to momentum) also plays a role – for example : in emergency situations a light passenger car doing in the order of 100km/h needs about 60m to stop, a truck weighing less than 5t would require about 70m and a truck weighing between 5t and 10t would require in the order of 80-90m (both doing about 100km/h). (In all these cases vehicles do not go into a skid situation and distances given do not include driver observation and decision distances).

Speed plays a major role in driver observation, recognition, decision and reaction time. In the case of a hazard or an incident on the road, the driver of a medium size motorcar driving at a speed of 120 km/h will need a total distance of about 227 metres from the point of observing a hazard and taking evasive action until the vehicle comes to a standstill. For a driver driving at a speed of 180 km/h this distance more than doubles to about 480 metres. Information on the total observation, recognition, decision and reaction distances required for various sized motorcars and speeds on a flat section of road are given in the graph below.

 

 

Required Stopping Distance - metres
Decision distance plus Action distance
Speed
km/h
Small
Car
Medium
Car
Large
Car
Heavy
Vehicle
60 60 66 77 116
70 78 86 101 154
80 99 109 129 197
90 121 135 159 246
100 146 163 193 300
110 174 193 230 359
120 203 227 271 424
130 235 263 314 495
140 269 301 361 570

 

 

Required Stopping Time - metres
Decision Time plus Action Time
Speed
km/h
Small
Car
Medium
Car
Large
Car
Heavy
Vehicle
60 5.73 6.44 7.76 12.37
70 6.50 7.32 8.87 14.24
80 7.27 8.21 9.97 16.11
90 8.03 9.09 11.07 17.98
100 8.80 9.97 12.18 19.86
110 9.56 10.86 13.28 21.73
120 10.33 11.74 14.38 23.60
130 11.09 12.62 15.49 25.47
140 11.86 13.51 16.59 27.34

 

Also View:

Brakes/Braking and Road Safety

 

Loading...

Search Road Safety Articles

Latest Pages

Hijack Prevention Guidelines

Hijack Prevention Guidelines

Introduction: It has become increasingly difficult to steal motor vehicles with all the anti-theft devices, such as immobilisers, gear locks, etc. These steps have resulted in a dramatic increase in vehicle hijackings. The hijacker has the element of surprise and this is a concern. The increasing

Read More

ABC of Accident and Crash Investigation

ABC of Accident and Crash Investigation

Stanley Bezuidenhout is an internationally experienced crash investigator, crime scene analyst, court expert, author, trainer, and public speaker. He has committed more than 20 years of his extensive career to crash investigation and expert services in many countries, including the SADC Region of Africa,

Read More

Analysis of crashing into a heap of sand through crash investigation

Analysis of crashing into a heap of sand through crash investigation

A Dashcam video has been doing the rounds on Social Media, showing the driver of a Jeep driving on the R30 between Bothaville and Odendaalsrus on Friday, 20 May 2022, in darkness. The video shows the time to be 05h26 and the vehicle to be driving at a speed of 100Km/h. The next minute, a literal heap

Read More

Road Safety Conferences

Road Safety Conferences

The Arrive Alive website supports those individuals and institutions who take the initiative to arrange road safety conferences in South Africa. We believe that this contributes to greater awareness of road safety and could assist in planning effective road safety strategies. 14th Annual Leadership

Read More

Standard Bank and Fuel Cards, Fleet Cards and Safety from Fraud

Standard Bank and Fuel Cards, Fleet Cards and Safety from Fraud

What are the best measures from the side of the bank to combat fraud with a garage/ petrol card? A robust and state of the art fleet management system is key to assisting customers to manage fleet expenses and combat fraud. In 2010 Standard Bank Fleet Management pioneered and led an industry initiative

Read More

Safe Driving in Heavy Traffic

Safe Driving in Heavy Traffic

Introduction As urbanisation drives many to the cities and vehicle ownership increases, road users have to prepare themselves with the skills and attitude required to drive in heavy traffic much more often. Heavy traffic could be caused by numerous factors including: Usual rush-hour /

Read More

Load More Pages

Partners

View All