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

The Emergency First Aid Kit and Safety on the Road

The Emergency First Aid Kit and Safety on the Road

We should always do our best to be prepared to respond to any emergency. Even though we may not be trained medical professionals there are often small bits of assistance we can provide with first aid and effective and fast response to smaller emergencies. We always advise motorists to travel with

Read More

Motorcyclists and Safely Sharing the Roads with Trucks

Motorcyclists and Safely Sharing the Roads with Trucks

Motorcyclists are at constant risk, operating their motorcycles for recreational rides and business commuting. The condition of our roads, and traffic congestion, pose a very dynamic threat to life on two wheels. Trucks are even more so, especially when the roadworthiness of the truck, the competency

Read More

Trucking Wellness & HIV Treatment

Trucking Wellness & HIV Treatment

Introduction Trucking Wellness (TW) is an initiative of the National Bargaining Council for the Road Freight and Logistics Industry (NBCRFLI), which was launched in 1999. The aim of Trucking Wellness is to provide primary healthcare to those employed within the Road Freight and Logistics (RFL)

Read More

Eating behind the Steering Wheel and Distracted Driving

Eating behind the Steering Wheel and Distracted Driving

Introduction The first thought for most on distracted driving is about texting while driving and drunk driving. Eating while driving is, however, one of the most common forms of distracted driving. With a fast-paced modern life and drivers rushing from one responsibility to another fast food and

Read More

Safe Driving and Preventing Jackknife Crashes

Safe Driving and Preventing Jackknife Crashes

What are jackknife crashes and how can we adjust our driving to prevent these crashes? We approached a few industry experts on driver training and crash investigation to gain some important insights! What is a jackknife crash and how does it happen? Jackknife crashes are, unfortunately, among the

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

Load More Pages

Partners

View All