During driver’s ed, students preparing to get behind the wheel of a car are taught about how long it can take to stop a car to avoid an impending crash, with the goal of emphasizing a safe following distance.

At Lake of the Ozarks—a place with more boats than cars—boaters may be more prone to wonder how quickly a Boat can stop! The answer: never quickly enough. But a boater who understands his or her reaction time and the best techniques to avoid a collision is best equipped for a safe, fun day on the water.

Speed is the third leading cause of boat collisions with shores, seawalls, docks, or another boat, according to the National Association of State Boating Law Administrators (NASBLA). In a recent five-year period and a recorded total of 25,469 boat accidents nationwide, the first two primary causes are operator inattention and careless or reckless operation. 

The actual time and distance required to stop a boat plays into both of those.

That’s why the best collision avoidance technique is not trying to stop, but steering out of the danger. According to Retired Missouri State Water Patrol Captain Gary Haupt, changing the course of the boat will always result in the quickest collision avoidance result.

This may be combined with reducing the throttle to slow the boat. However, a craft with jet drive such as a PWC will lose all steering control without forward thrust so operator experience and focus are essentials.  

Every automobile driver is familiar with the stopping distance charts in the driver license manual. They factor in the reaction time to apply brakes and calculate the actual distance it will take the car to stop while braking. For cars, fairly simple calculations yield an exact number for both reaction distance and total stopping distance for any given speed.

But on water, exact calculations are not possible. The algebraic formula for stopping distance in a car relies upon a co-efficient of friction value for a given road surface that does not exist on water. Plus, boats have no brakes. Reversing the props is the only way for a boater to increase stopping efficiency.

Here’s a breakdown of the time it takes to detect a potential problem ahead and get the boat moving (or slowing) in a way that will avoid it.

Perception/Response Time: 2.5 – 3 seconds

Reaction time involves both perception of a given threat and response time to recognize the best threat avoidance maneuver for that situation. However, perception and judgment are tough to measure and are affected by variables such as age, situational complexities, and a number of possible responses from which to choose. Nevertheless, the most common number assigned to perception/response (PR) time for boat operators is 2.5 to 3 seconds, according to Haupt, who is the program manager and lead Instructor for NASBLA’s Boat Accident Investigation Course. 

Haupt explains the water is far more complex than the road, because while an auto driver is confined to a lane and the possible threats are in relation to it, a boat operator must keep a vigilant lookout for a full 360 degrees. Further complicating response times are increased distractions in a water environment, both inside and outside the vessel.

Another complicating factor is operator inexperience. Driving a boat a few weekends out of the season is vastly different from driving a car every day. The automatic, practiced response of moving the right foot from gas to brake pedal in a car is not present for the occasional boat operator. Calculating a threat and deciding to pull back the throttles or turn the wheel to steer out of danger are less automatic reactions because they are infrequently practiced, and this was observed by NASBLA in tests using many students at a helm simulator. The results showed 2.5 to 3 seconds is a typical reaction time for most people who are paying reasonable attention to recognize a danger and choose an appropriate response.

Reaching For The Throttle: .5 second

Another .5 second passes while operators are moving their hand. 

So a total of 3.5 seconds passes before the operator begins to change the boat controls by pulling the throttle back and/or taking the appropriate steering avoidance maneuver.

Boat’s Response: up to 1 second

In addition to the above times, the boat’s response to the helm is never instantaneous. There may be as much as an additional second before the vessel responds. 

According to Haupt, this can result in an accumulated response time of 5 seconds or more.

Total: 4–5+ seconds

A 25-foot boat traveling on the lake at 50 MPH, could travel 367 feet—or 15 boat lengths—in the time it takes the operator to pull the throttle or turn the wheel.

Of course, the full response time of 5 seconds assumes the operator is paying full attention to the task of driving and is looking far down the channel for possible dangers such as other craft coming out of coves or quickly turning into his or her path.

Two boats, traveling toward each other at 50 MPH, will have a combined closing speed of 100 mph or 150 feet per second. In the 5 seconds it takes the operator to respond to the danger, the two closing boats could have covered 750 feet, or more than 1/8 of a mile.

And that’s not actual stopping time; it’s only a measurement of when the boat might begin slowing down (or navigating) from the time the operator first sees a potential danger. Boats don’t have brakes, so it could take quite a while for the boat to actually come to a stop. 

Depth Perception

For a person to quickly determine how fast something is moving, they need to be able to estimate its size. Most cars on the road are pretty much the same size. A Honda Civic is around 15 feet long and 6 feet wide, while full-sized Chevy Impala is 2 feet longer but about the same width. But anyone who’s boated at Lake of the Ozarks knows boat sizes vary dramatically. Boats on the Lake can vary from 18 to 50 feet (or more!), making it more complicated and more time consuming for boaters to judge distance.

Depth perception on the water is more difficult than on land. There are no reference points and no known comparisons such as standard and well-striped traffic lanes.

Lake of the Ozarks does not have a day-time speed limit on the water. The lake has literally hundreds of boats capable of sustained speeds over 100 MPH. Local insurance agent Chris Wagner with WIA Marine Insurance specializes in boat insurance covering those craft which are capable of speeds up to 180 MPH. 

Being aware of the operating capabilities of these vessels is critical for anyone operating one of them, especially because the actual distance it takes for the boat to stop is a complete unknown. There is no way to put an accurate number on the stopping distance because of the many variables such as operator experience and reaction times as well as water condition, hull design, and weight of the boat.

The take-away is: safe boating is no accident. Knowing the capabilities and limitations of the vessel, being fully aware of the potential threats on the water, and knowing how to avoid a collision means everyone goes home safely at the end of a fun day on the lake.