Speeding Calculator

Speeding Calculator
Hydroplaning Info
What is this?

This calculator evaluates your speeding tendency and shows how little time is actually saved over short distances.

How do I use this?

The distance is the constant value. Enter either the average speed or the time it takes you to travel that distance. Then hit the calculate button next to the variable you want to solve for. Select the checkbox for adjusting the calculations to handle for lights that you encounter. Select how many lights on your route and an average time spent at each light.

Distance (miles):
Time (minutes):    
Speed (mph):    

Traffic Lights?
-- Quantity:
-- Seconds per:  

Last updated: 3/27/2009

When I originally wrote this I used to live 15 miles from work and it took me 30 minutes to drive it. Enter 15 for distance, enter 30 for time, and press the calculate button next to speed (the value I want to solve for). My average speed appears as 30 mph even though most of my trip is at the speed limit of 55 mph. So the traffic lights and other traffic shoot my average to hell.

To adjust for the traffic lights, check the box and enter how many lights you drive through and how many seconds to allot per light. I go through 24 traffic lights and have decided on making 20 seconds the default, so I'll try that. This gives me an average speed of 41 mph, which is probably realistic seeing that some segments are at 30 mph and others are at 35 mph.

You may want to play with these figures until you find amounts that work for your driving style. Then you can get more accurate data.

In order to shave 5 minutes off of my travel time; using the above data, enter 25 for minutes and press calculate next to speed. We get 53 mph (52.9 to be exact, if you try the formula via a calculator). So I would need to increase my average speed 12 mph over the entire route in order to compensate for the traffic lights and other traffic along my route. Seeing that most police officers grab people in excess of 5 mph over the speed limit (higher being a sweeter target), this puts us right in their sights.

The moral of this story: If you are going to be late, just accept it. Unless your trip is over a very long distance you won't really gain much. You'll have to leave earlier to get there on time. So, why do people speed? Probably because they haven't done the math, or maybe they just like going fast. You tell me.

I was planning on putting a hydroplaning calculation tool here but may not. After doing some research, the formulas used to calculate this differ depending upon tread depth, tire surface area, tread design, vehicle weight, depth of water, and even the consistency of water.

Most people, myself included, would not be able to enter the majority of the variables. So, here's the best I could find to play with.

Hydroplaning speed = 10.27 * Sqrt(tire pressure)

Most car tires are pressurized to 35 psi, so hydroplaning can occur at 60.76 mph. You can plainly see the importance of keeping your tires properly inflated since hydroplaning speed will decrease with a decrease in pressure. By how much?

34 psi = 59.88 mph
30 psi = 56.25 mph
25 psi = 51.35 mph

A quick way to estimate this is to use 61 mph for 35 psi and subtract 1 mph for every psi lost (1 for 1 exchange). I like easy math.