Black Ice in Sandy: Where It Forms First and What to Do When You Find It

Black ice is a thin, transparent layer of ice on the road surface, and the Utah Highway Patrol is blunt about the name: despite its nickname, black ice is actually clear. What you are looking at is the dark asphalt underneath it. UHP compares it to a glaze and notes that it forms on all kinds of surfaces, roads and sidewalks and driveways alike.

It forms, in UHP's words, when recent rain or snowmelt comes into contact with freezing temperatures. A dry cold snap rarely produces it. A thaw followed by a hard freeze almost always does. Three ordinary Sandy situations supply the water:

Bridges and overpasses glaze first, and UHP says so directly: bridges and overpasses may be more susceptible to icing. A bridge deck loses heat from above and below, with no warm ground underneath to hold its temperature up. Every I-15 overpass in Sandy, from 9000 South to 10600 South to the Bangerter Highway ramps, can be slick while the road leading onto it is merely wet. A patch that looks like a wet spot on an otherwise dry deck at six in the morning is usually not a wet spot, and UHP's own advice is to treat water-looking patches as possible ice.

Curbs and center dividers are the other reliable spot. UHP notes that black ice can form on any road, and also along curbs and highway center dividers. That matters on Sandy's wide arterials, where meltwater runs to the gutter and sits. State Street, 700 East and Highland Drive all collect runoff along the curb line, and the lane closest to it freezes first while the inside lanes stay clear.

Then there is the geography. Sandy's east side climbs toward the mouths of Big and Little Cottonwood, and the Wasatch stands directly east of town, so the sun clears the ridgeline later than the clock suggests. Roads along Wasatch Boulevard and the approaches to SR-210 and SR-190 sit in shade well into the morning, and shaded pavement holds an overnight freeze long after the valley floor has given it up.

The dangerous window opens after dark and often survives breakfast. UHP puts it plainly: while black ice is more prevalent at night, it can often stick around for the morning commute. The mechanism is the melt-and-refreeze cycle that Utah winters are built on. A bright afternoon in the high thirties melts snow along the shoulders and driveways, the temperature falls once the sun goes, and whatever ran onto the pavement sets where it stopped.

Which is why the worst mornings in Sandy often follow the nicest afternoons rather than the storms. During a storm the road is visibly white and everybody drives like it. Two days later the lanes look clear, the sky is blue, nobody is thinking about traction, and there is a sheet waiting on the overpass deck.

Enough that the posted limit stops being the reference point. UHP's winter driving guide says that if it is wet, snowy or icy you should be going under the speed limit, and it names the cause without hedging: people driving too fast is the main cause of crashes in winter. Federal Highway Administration figures give a sense of scale. Average arterial speeds fall by 30 to 40 percent on snowy or slushy pavement, and freeway speeds drop by 5 to 40 percent in heavy snow.

Stopping distance moves with it. Snow and ice reduce pavement friction and vehicle maneuverability, in FHWA's wording, so the gap you keep behind the car ahead in July is not the gap you need in January. NHTSA's winter guidance is to increase your following distance enough that you will have plenty of time to stop for the vehicles ahead of you. On a glazed surface that means several times the gap that feels normal.

Ease off the accelerator and steer where the back of the car is going. That is the Utah Highway Patrol's instruction word for word: if you start to skid, ease off the gas and turn in the direction the back of your car is going. Do not stab the brakes and do not throw the wheel the other way. UHP's broader rule for slick pavement is to accelerate slowly, brake gently and avoid turning quickly, and all three of those are really the same instruction about how fast you ask the tires for something.

If you do have to brake hard, what happens next depends on the car. NHTSA says that with antilock brakes you apply firm, continuous pressure to the brake pedal, and that without them you may need to pump the brakes if you feel the wheels starting to lock up. Nearly everything on the road in Sandy has ABS. The pedal will buzz and push back under your foot, and that is the system working rather than a fault to react to.

The patch is usually short. Most black ice around here is a car length or two on a bridge joint, a shaded curve or a gutter line, so a car that is not being fought will often find grip again on its own. The damage tends to come from the correction rather than the slide.

If it ends with the car off the pavement or hard against a curb, stay belted until you have looked at what is coming up behind you. UHP warns that crashes on icy roads often happen in clusters at the same spot, which is the part people underestimate: the ice that caught you is still there for the next driver, and standing on the shoulder is dangerous even on a dry day. Getting out to push on ice generally polishes it. A winch out and recovery or snow and ice recovery crew can pull the car back onto the road without spinning the tires, and flatbed towing is the safer call if anything underneath took the hit.

Rarely, and almost never in time. It is clear, so what reaches your eye is the road surface underneath, which is where the name comes from even though the ice itself has no color. The usable tell is context rather than appearance. A patch that looks wet on a road that is otherwise dry, on a morning below freezing, is almost certainly ice. Spray disappearing from behind the tires of the car ahead is another sign that the water on the road has stopped being water.

It helps you get moving and does nothing for stopping or turning. Drive type changes how engine power reaches the ground; it does not change the grip available between a tire and a sheet of ice. That is why all-wheel-drive vehicles end up off Sandy roads every winter alongside everything else. Tread, temperature and speed decide what happens on ice, not the badge on the tailgate.

Bridges and overpasses, shaded curves and the curb lane. UHP lists bridges and overpasses as more susceptible to icing, along with curbs and highway center dividers. In Sandy that points straight at the I-15 overpasses, the shaded approaches toward the Cottonwood canyon mouths, and the gutter side of the wide arterials where snowmelt collects and refreezes overnight.

Stay in the vehicle with your belt fastened, get the hazards on, and call for a tow instead of trying to drive it out. NHTSA's advice for a stuck or stalled vehicle in winter is to stay with the car and not overexert yourself, which on a bank of frozen slush is also the advice that keeps you out of the traffic lane. Towing Sandy runs snow and ice recovery and 24/7 towing across Sandy and Salt Lake County right through the winter.