Stopping Distances

 

An article by Eddie Wren

(Amended, August 2004)

 

With the advent of better brakes, vehicle stopping distances have reduced somewhat over the years but it has to be remembered that, no matter how good the brakes and tires, the laws of physics don’t change.

The most important point for any driver to remember is that if you double your speed — say from 30mph to 60mph — your braking distance does not become twice as long, it becomes four times as far.

Because there are differences between various vehicles, the following tables are for guidance only. The biggest factor in stopping distances is the speed at which a driver reacts to seeing the hazard in question. Under ordinary driving conditions, very few drivers indeed can get onto the brakes within half a second, and two-thirds of a second to a full second is more typical.2

Most frighteningly, Australian research has shown that the very people we expect to have the fastest reactions — young drivers — are particularly prone to effectively ‘freeze up’ with fear, at the sight of an unexpected hazard ahead, and their reaction time can therefore exceed two seconds.

Lastly, don’t forget that when you read the 60-0mph figures in literature for new cars, the automaker is giving you only the braking distance, not the overall stopping distance.

 

Stopping Distances for Dry Pavement/Road 1

 

SpeedThinking

Distance 2

Braking

Distance

Overall

Stopping Distance

Comparisons

20 mph20 feet

  20 feet

  40 feet
30 mph30 feet  45 feet  75 feetFull  length of  tractor/semi-trailer or articulated wagon
40 mph40 feet  80 feet120 feet
50 mph50 feet125 feet175 feet
60 mph60 feet180 feet240 feet
70 mph70 feet245 feet315 feet(USA = “Touchdown !”)
80 mph80 feet320 feet400 feetAbout six semi-trailer or articulated wagon lengths 3

 

(Copyright ©, Eddie Wren, and Drive and Stay Alive, Inc., 2003 onwards)

 

Stopping Distances for Wet Pavement/Road 1

 

 

SpeedThinking

Distance 2

Possible Braking

Distance

Overall Stopping Distance Can Be:

Comparisons

20 mph20 feet

  40 feet

  60 feet
30 mph30 feet  90 feet120 feet
40 mph40 feet160 feet200 feet
50 mph50 feet250 feet300 feet(USA = Touchdown !)
60 mph60 feet360 feet420 feet
70 mph70 feet490 feet560 feet
80 mph80 feet640 feet720 feetAlmost two and a half American Football fields 3

 

(Copyright ©, Eddie Wren, and Drive and Stay Alive, Inc., 2003 onwards)

Remember – 1: When the road is icy or covered with compacted snow, or diesel fuel has been spilled (which is a particular risk near certain gas stations) the ‘braking distance’ for your vehicle can be as much as ten times further than for dry roads/pavement.

Remember – 2: ……………Any fool can drive fast enough to be dangerous!

Notes

1  For non-US readers, ‘pavement’ is the American word for the road surface. We are not referring to the British meaning of the word, which is the same as the American ‘sidewalk’.

2  The ‘thinking distances’ shown allow for two-thirds of a second reaction time. This varies from one driver to another and for individuals who are ill, tired or simply not concentrating, it can be much longer.

3  The 80mph examples are not here to condone breaking any speed limits, rather to illustrate the extra dangers faced by, and caused by, those people who exceed the usual highway limits.