[USA] Bridge ices before road

[c2R]

so... a question that I wondered is why the fact that bridge ices before road signed literally everywhere on the interstates in the US....
In the UK, such signs are only really included where the road is particularly suspectible to it... and why just this particular hazard rather than a multitude of others?

[mikehindsonevans]

so... a question that I wondered is why the fact that bridge ices before road signed literally everywhere on the interstates in the US....
In the UK, such signs are only really included where the road is particularly suspectible to it... and why just this particular hazard rather than a multitude of others?

As my pen-friend explained it to me before we embarked on a trip down the Interstate: "Many bridges have steel lattice-grid surfaces over the rivers, which help drainage of the road (with less run-off) but this means that the temperature will drop faster than on the main pavement" (she meant, of course, "carriageway").

[c2R]

Cheers, yes, I know that it is a fact that it does happen and the reasons why... I was just surprised at the sheer number of these signs all across the country compared with Europe... and also that this particular hazard has been singled out for signage but many others have not...

[Truvelo]

The road surface on bridges in the US is the opposite to here. Our bridges have asphalt whereas theirs have concrete. For example the M54 which is concrete between J2-4 has asphalt on all the bridge decks. In the US all the asphalt freeways have concrete on the bridges.

As for signage some states word it differently such as "Watch for ice on bridges".

[KeithW]

The major factor in the USA s that they see much greater extremes in temperature not only season to season but from hour to hour. In late September 1988 I made my first visit to Nevada for a computer conference at Stateline which is on Lake Tahoe near the border with California, the temperature at 8 PM when I checked in was still around 25 deg C. On the last day after the conference ended I sat on the outside bar terrace with colleagues where it was warm enough that nobody needed a jacket. The next morning when I checked out a cold front had arrived from Canada and it was -4 C. It started snowing on the drive to Reno airport and the roads were heavily iced. In Ohio where cold weather in winter is the norm such signs were much rarer especially away from the Interstates.

[ScottB5411]

Ice storms being the worse culprit. Ice storms are commonplace in the USA, right down to the gulf coast and I've never really seen anything like it in Britain. As has been stated above, the bridges mainly having a concrete surface are a lot colder and where an ice storm is occurring, it may not freeze on the asphalt but the bridges are just sheets of ice, quite often you see wrecked vehicles right after bridges. Lack of driver training being the culprit as they just don't lift off for the bridge and then have no clue how to correct the now sliding vehicle, despite them thinking they are the world's best driver and can drive at 90 in those conditions

[Ruperts Trooper]

My basic physics would suggest that part of the difference between icing on bridge surfaces and ordinary road surfaces is that the latter is built on solid ground which acts as a heat sink so loses little heat donwards whereas a bridge loses heat both up and down.

[RichardA626]

I remember my last time in the USA almost every bridge in Arkansas had signs on warnings of icing.

Freezing rain is a problem in the states near the great lakes, where rain can turn into ice on contact with the ground.

[KeithW]

Ice storms being the worse culprit. Ice storms are commonplace in the USA, right down to the gulf coast and I've never really seen anything like it in Britain. As has been stated above, the bridges mainly having a concrete surface are a lot colder and where an ice storm is occurring, it may not freeze on the asphalt but the bridges are just sheets of ice, quite often you see wrecked vehicles right after bridges. Lack of driver training being the culprit as they just don't lift off for the bridge and then have no clue how to correct the now sliding vehicle, despite them thinking they are the world's best driver and can drive at 90 in those conditions

Yes I remember ice storms from time in Ohio. Chipping off half an inch of ice just so you get in the car is no fun at all and you can forget about the common British practice of pouring hot water on it, all that does at -20 is make the ice thicker.

[trickstat]

Freezing rain is a problem in the states near the great lakes, where rain can turn into ice on contact with the ground.

I've encountered this once in the UK as a pedestrian*, I can remember the pavements being very slippery without looking obviously icy.

*I was glad I wasn't driving.

[J N Winkler]

There is enormous variation among US states in how heavily "Bridge Ices Before Road" is used. My home state, Kansas, does not use it at all, while neighboring Oklahoma uses it for every single bridge. I personally think these signs should not be posted and drivers should be expected to know the basic, empirically observed fact that bridges freeze first, even if they do not go to the lengths I do and pull up real-time RWIS data to sample bridge deck temperature.

Some have suggested that in some states the bridge-icing signs function as substitutes for snowplow "blade raise" markers for bridge rails. These markers are used in some northern states (e.g., Minnesota) but not others (e.g., Wisconsin, Michigan).

[RichardA626]

I remember Tennessee & Arkansas both seemed to put up signs warning of bridges icing up.