If you want a safe and reasonable answer to that question, have I got a chart for you!
This chart is based on a deceleration rate of 12 fpsps and .75 second reaction time... It's international in scope (shows MPH and KPH) with results in seconds to slow and feet travelled while slowing... So you can see whether you'll be able to slow down to the PSL in time.
Since the 12 fpsps is conservative, it should be possible for folks with worn out tires, or on rain slick roads, or with bad brakes, but not more than one of the variables... and all bets are off on snow or ice.
The 3/4 second reaction time is a national average... some will do better, some worse...
All of that said, here is a disclaimer for you, too:
Use the chart at your own risk. I do not guarantee that it will represent your driving capabilities or work with your vehicle. As in life, your mileage may vary... I will not pay speeding tickets if you rely on this chart to save your butt... I offer it only as an exercise in mathematics and what could be possible if you decelerate in time! Have fun with it!
Two varieties:
An excel spreadsheet for your own computer
http://www.guysoflidar.com/files/speed_sheet3.xls
A wep page you can see right away (on a PC: right click, open in new window) (on a mac, go punt! I don't know, honest!)
http://www.guysoflidar.com/files/speed_reduction.htm
Thanks to Jimbonzzz for hosting these files on the Guys of Lidar site!
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