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

Tyre Safety

Tyre Safety

Tyre Safety Tyre failure is a vital factor in thousands of road accidents every year. Research by the CSIR indicates that nearly 20% of accidents involving minibuses have tyre failure as a contributing factor. It won't help if you have the best brakes on the market, but your tyres are worn. When

Read More

Safe Driving on Gravel Roads

Safe Driving on Gravel Roads

Introduction Many licensed drivers have never driven on gravel roads or are inexperienced and unprepared for the unique challenges when doing so. This inexperience and lack of safety awareness result in too many fatal crashes and injuries on gravel roads in our rural areas. We must equip ourselves

Read More

Safe Driving on Roads with Potholes and Avoiding Pothole Damage

Safe Driving on Roads with Potholes and Avoiding Pothole Damage

Introduction We have all been confronted by poor road conditions and the threat of the dreaded pothole. It is especially on our rural roads and after the rainy seasons that the road surface comes under pressure and the cracks and holes in the road surface start to appear. In some areas, the road

Read More

Drunk Driving and Road Safety

Drunk Driving and Road Safety

Drunk Driving and Road Safety Drunk Driving is one of the biggest threats to Road Safety in South Africa. Research indicates that 50% of people who die on the roads have a blood alcohol concentration above 0.05 gram per 100 millilitres. Brief Summary: Legislation: The National Road Traffic

Read More

Compliance in the Road Freight Transport Industry in South Africa

Compliance in the Road Freight Transport Industry in South Africa

The South African freight transportation landscape fundamentally differs from that of the rest of the globe. In most other countries the fleet sizes comprise mostly of the owner of the transport business, who is also an “owner-driver” on one of his vehicles and maybe another couple of vehicles,

Read More

Treatment of and Response to Cuts and Bruises

Treatment of and Response to Cuts and Bruises

The skin is the largest organ of the human body, about 2m square in surface area and has several functions. It is also a barrier which provides protection from infection and heat loss. We need to remember that most cuts are minor and require little attention. The size of cuts, the number of cuts (also

Read More

Load More Pages

Partners

View All