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About Terry Godchaux
Expertise
I can answer questions about vehicle safety issues, vehicular counter-terrorism training, police pursuits in general (specifically for California), emergency response in general (specifically for California), criminal justice, and police academy training.
Experience
I have recently retired as a Deputy Sheriff from California. I have served in Patrol and special Investigations.
My last position for 10 years was assigned to our Regional Training Center at the Sheriff's/Police Academy. I taught at the Academy and administrated the Emergency Vehicle Operations Course (EVOC). I also was a subject matter expert and served as a member of CalPOST.
My specific training and expertise resides in vehicle operations, vehicle safety, code-3,pursuit, and counter-terrorism operations.
Organizations
Former P.O.S.T. Board Member for EVOC
Former P.O.S.T. Board Member for Simulations
Former P.O.S.T. Board Member for the Sheriff’s and Police Academy
Former Instructor for the Las Positas College (A.J. EVOC)
Former Instructor for San Joaquin Delta College (A.J. EVOC)
Former Lead Instructor for EVOC at the ACSO Police Academy
Publications
Numerous within the S/O I had worked for.
Education/Credentials
Baccalaureate Degree
Management and Administration Certificate
Basic California P.O.S.T. Certificate
Intermediate California P.O.S.T. Certificate
Advanced California P.O.S.T. Certificate
California P.O.S.T. Crises Management
California P.O.S.T. Crime Prevention Training
California P.O.S.T. Advanced Crime Prevention Training
California P.O.S.T. Environmental Engineering School
California P.O.S.T. Drug Recognition Expert
California P.O.S.T. DARE Instructor
California P.O.S.T. Specialized Training Institute (CSTI) Tactical
California P.O.S.T. Firearms Instructor
California P.O.S.T. Driver Awareness Instructor (DAI)
California P.O.S.T. Pursuit Driving Training Instructor (DTI)
California P.O.S.T. Basic Motorcycle School
California P.O.S.T. Motorcycle Instructor
California P.O.S.T. Tactical Vehicle Instructor
California P.O.S.T. Dignitary Protection Instructor
California P.O.S.T. Counter-Terrorist Instructor
California P.O.S.T. Driver Simulator Instructor
California P.O.S.T. P.I.T. certification
Barricade Braking certification
Past/Present Clients
I currently work as a contract Instructor for the Jutice Department/MPRI when training needs concerning EVOC arise outside of the U.S.
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You are here: Experts > Parenting/Family > Protecting your Home and Family > Transportation and Vehicle Safety > Braking distance ratio by weight
Expert: Terry Godchaux - 10/30/2009
Question
Good day,
Is there a simple way to determine the difference in braking distance in a pick up that is empty or one with 500 or 1,000 lbs. on it.
Thank you
D.K. Welbourne
Answer
Hello D.K. and welcome to AllExperts!
By way of your question, it appears you have done your homework and have given up trying to find the answer on your own.
One of the reasons for not finding the information you're looking for is due to the complexity and many variables necessary for establishing data to your equation.
There are foundational facts to plug in such as:
PHYSICS:
Speed, mass, weight, coefficient of friction, temperature, basic unloaded center of gravity, placement of load in relationship to vehicle C.O.G., and weight transfer.
VEHICLE:
Front wheel drive, rear wheel drive, all wheel drive.
Suspension, vehicle clearance (ground to frame).
Tire type/size/configuration/percent inflation to rated pressure.
Brake type, configuration of brake type, sizes of rotor or drum, material formula and cooling.
ABS, Non-ABS, Air, vacuum or pressure system.
DRIVER:
Perception, Decision, and Reaction from on-view to maximum effective braking achieved.
Percent of effective braking.
CONDITIONS:
Type of roadway (asphalt/cement/old or new pavement).
Condition of roadway (damage/ruts/washboard effect).
Foreign objects on roadway (sand/gravel/liquid/etc).
Temperature effecting roadway coefficient of friction.
Grade of roadway (up/down), Lateral crowning, etc.
Straight inline braking or into a turn, and angle/percent of turn is this applies.
WEATHER:
Conditions present (rain, sleet, snow, ice), Dew point, and wind direction and speed.
While many online calculators and formulas exist, they ALL take some degree of averages into account as it is impossible for one simple rule of thumb to be anywhere close to being accurate. Even those that attempt this usually never account for percentage of weight from the vehicles basic weight to the maximum rated weight.
Finally, stopping distances are greatly skewed by the type of brakes and tires used. Some very large and heavily loaded trucks can have unexpectedly good stopping distances due to engineering and specifics of its braking system.
This is why it takes a traffic accident investigator several hours using manuals, graphs and computers to figure out these facts.
The only simple answer I can possibly give is that every braking system is designed to handle its maximum rated load. Some vehicles such as light rated trucks with a light rear end stop faster with an allowable rated load then with no load.
I wish I could be more succinct and helpful, but the process for getting this information is anything but simple, and this is why you probably have not found one as yet.
The best simple calculator I have seen online is at:
http://hyperphysics.phy-astr.gsu.edu/HBASE/crstp.html
Keep in mind that it still uses many rule of thumb generalizations and still doesn't answer your basic question at all.
I hope this has helped D.K. / Have a wonderful day!
Terry
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