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

Cellular Technology and Road Safety

Cellular Technology and Road Safety

Background Information The dangers of cellular phones to road safety are well debated and documented. It is an offence to hold and use a cellphone or other electronic communication device such as BlackBerry, Personal Digital Assistant (PDA) etc whilst driving. The only defense for a person charged

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

Escape and Safety from Vehicle Fire

Escape and Safety from Vehicle Fire

Introduction and Overview Tens of thousands of lives have been lost globally in the last few decades due to car entrapment deaths. In this section we will analyze the threat of vehicle fires and provide advice on how to act in these emergencies. Data from the United States reveals the importance

Read More

Investigation of the Contributing Factors to Vehicle Fire

Investigation of the Contributing Factors to Vehicle Fire

In this article, Stan Bezuidenhout from IBF Investigations gives us the low-down on vehicle fires. As a Forensic Specialist with more than 20 years of experience responding to and investigating road traffic collisions, he has investigated more than his fair share of vehicle fires. This is his take on

Read More

Road Safety with Arrive Alive on Twitter: Why does it Matter? What have we Learned?

Road Safety with Arrive Alive on Twitter: Why does it Matter? What have we Learned?

Introduction It has taken a while but we are proud to confirm that the Twitter handle of the Arrive Alive Online Initiative @_ArriveAlive has reached the 280,000 followers mark. This number is a bit of a milestone and an indication that we may be heading on the right path to reaching an online

Read More

The Health Risks of Exposure to Dust

The Health Risks of Exposure to Dust

First responders come across many situations where dust is present, such as factories, dusty roads, concrete-cutting facilities and even workshops. Dust is found in many places on a job site and can be hazardous to your health a somewhat detailed explanation of these hazards is explained below. The

Read More

Load More Pages

Partners

View All