Road Quality Classification
Whenever hazardous weather occurs, there's always discussion about the expected impacts on travel and commutes. However, just saying that "travel is discouraged" isn't particularly informative since some combinations of precipitation (especially winter precipitation) are more impactful than others. And, even within the realm of winter precipitation specifically, there are some combinations of ice and snow that create especially slick and treacherous conditions.
Accordingly, something that might improve public messaging of road conditions would be a 0-5 scale representing what the road quality is expected to be and how feasible it is to drive somewhere. That way, there's some exact perspective on whether travel should be attempted and how difficult it will be to get from Point A to Point B.
Generally speaking, driving becomes more dangerous as the depth of standing water increases, because deeper water leads to an increased risk of hydroplaning. However, standing water depths greater than 1 foot can potentially cause a vehicle to stall or even be swept away. Depths greater than 4 feet become extremely hazardous to vehicles since most vehicles would be completely inundated by floodwaters this deep.
As far as winter precipitation is concerned; snow, sleet, and slush are generally easier to drive on than sheets of solid ice. However, a respectably common occurrence is a round of freezing rain followed by sleet and wet snowflakes. A thin layer of snow, sleet, and slush on top of solid ice creates a particularly dangerous surface since car tires will be quick to brush aside the slush, but will do so unevenly, which will impart a significant imbalance of friction on the vehicle and thereby greatly increase the likelihood of losing total control. Another particularly dangerous circumstance is a "black ice", which is a layer of ice so thin that it looks like ordinary water but is in fact deceptively slick. If strong winds also coincide with slick roads, the wind will also push the vehicle around, further increasing the likelihood of an uncontrollable skid.
Finally, visibility is another consideration when assessing the viability of travel. Generally speaking, visibility becomes somewhat problematic when drivers can only see a couple miles in front of them when driving at highway speeds, but such visibilities don't usually cause complications when driving below highway speeds. Visibility less than a quarter mile will complicate any driving, and visibilities near 0 become dangerous, especially when strong winds are present.
With all that in mind, here is a potential road quality classification scheme:
| Quality | Category | General Description | Road Surface | Water Depth | Snow Coverage | Ice Coverage | Visibility |
|---|---|---|---|---|---|---|---|
| 5 | Optimal | Ordinary levels of caution warranted. | Generally smooth road surface, any cracks or potholes will barely be noticeable and won't require reducing speed. | Completely dry roads or isolated wet patches that will impact, at most, one tire at a time. | No consequential snow on roads. | No consequential ice on roads. | Visibility greater than 5 miles. |
| 4 | Good | Safe travel is possible with slightly increased caution. | A few cracks or potholes are present, which may require slowing down to avoid vehicle damage. | Roads damp (no standing water) with little to no oil. | Isolated patches of snow or slush with depths of 1" or less, or snowflakes that briefly accumulate on the road before melting. | Isolated icy patches that are easy to avoid and affect, at most, one tire at a time. | Visibility is 0.25-5 miles. |
| 3 | Passable | Safe travel is possible with extensive caution. | Disruptive cracks and potholes are prevalent. Some sections of road may be missing, blocked, or unstable; but it is possible to safely navigate around any such sections if great care is taken. | Roads damp with a mixture of water and oil (caused by rain after a long period of dry conditions) or generally covered with less than 1 foot of standing water, which will require reducing speed to minimize the risk of skidding or hydroplaning. | Patches of snow or slush with depths of 1"-6" that will mostly affect all tires. | Icy patches cover a majority of the road surface, but can still mostly be avoided by an alert driver. This can also include scenarios when overpasses are completed covered with ice, but grounded roads are just damp. | Visibility less than 0.25 miles but not near 0. |
| 2 | Poor | Travel should be avoided unless it is for something essential. | Large sections of road missing, blocked by obstructions, or damaged; and any such sections are also risky to navigate around. | Roads covered with water of approximately 1-2 feet deep, which means that vehicles may be swept away, and driving too quickly into the water may cause serious damage to the engine or the vehicle body. | Road surface completely covered with snow or slush with depths generally 6"-12". | Most or all tires will be in contact with solid ice that is easily visible. | Near 0 visibility. |
| 1 | Terrible | Travel should be avoided unless it is an imperative circumstance. | Roads are unstable and at risk of imminent structural failure. Missing sections or obstructions nearly impossible for drivers to see and properly react to. | Roads covered by water at depths of 2-4 feet or by rushing water 1-2 feet deep, which means that most vehicles will be swept away. | Thin layers of water, snow, and/or slush situated on top of solid ice or snow depths of at least 12". | Black ice from freezing fog/drizzle is prevalent or high (35+ mph) winds coupled with solid ice that is easily visible. | High (35+ mph) winds coupled with near 0 visibility. |
| 0 | Hazardous | Travel should not be attempted unless it is an imminent life-or-death situation. | Road completely destroyed with no stable ground to drive on. | Roads covered by water at depths over 4 feet or by rushing water 2-4 feet deep, which means that all vehicles will be instantly swept away and potentially inundated. | High (35+ mph) winds coupled with thin layers of water, snow, and/or slush situated on top of solid ice. | High (35+ mph) winds coupled with black ice from freezing fog/drizzle or severe (58+ mph) winds coupled with solid ice that is easily visible. | Severe (58+ mph) winds coupled with near 0 visibility. |
This particular scheme has 5 being the best and 0 being the worst, though it might also be worthwhile to reverse the order and call it a "travel danger index" instead of a "road quality index". Of course, the exact thresholds provided in the table can be adjusted based on regional readiness since municipalities that frequently witness snow have more resources to keep travel viable. The values provided are meant to be a general guideline.