Hydroplaning dangers

In a reprise of two accidents in 2011 and 2012, last Dec. 16 a bus traveling at high speed, in the rain, on the Skyway, drifted and crashed into a side rail, falling on a van traveling on the ground-level highway below, and killing 18 and injuring 16.  “Traffic investigators still have to determine” why the bus fell off the Skyway.  In the 2011 incident, the conductor narrated “how the bus seemed to be blown sideways by the wind.”  In the 2012 incident, the bus operator explained their drivers had just been retrained and the accident happened “only because the road was slippery.”

Keep in mind that the area of a tire in contact with the road, called the tire’s “footprint area,” is actually much smaller than it looks; typically, it is about the print of a size-9 shoe.  It is only that small area of each tire that prevents a vehicle from skidding or sliding out of control. It is easy to see why a vehicle, crossing a bridge flooded by a seemingly shallow depth of water rushing across the bridge, is often swept off the bridge; or why a bus speeding on a thin film of water loses a great deal of traction compared to when it is traveling on a dry road.

The three buses were not just speeding on thin films of water, because the rain created pools more than an inch deep on the uneven road surface. The website wiki.answers.com describes hydroplaning graphically: “A wedge of water is forced under the tire (by high speed and/or worn tire treads), which is lifted on a sheet of water.  The result is a complete loss of normal control by the driver and the vehicle will slide (with no road contact) until it collides with an obstacle or road traction is regained.”  A video from youtube.com, What To Do If You Hydroplane, recommends drivers to slow down to 60 percent of the usual dry road speed (e.g., if 100 kph is the norm in dry road conditions, under rainy conditions the maximum prudent speed limit would be 60 kph, assuming visibility allows that speed).

Unless bus companies are required to retrain their drivers to be aware of the danger of hydroplaning and how to drive in moderate and heavy rain, and unless maximum speed regulations posted on highways show a mandatory lower speed limit in rainy conditions, more deaths and injuries from accidents due to a lack of understanding of hydroplaning hazards will continue to occur.  The “obstacle” the next bus crashing through a center rail or island could be hurtling toward—God forbid!—may be you and your companions in another vehicle.

—BENJAMIN AGUNOD,

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