black ice

Commuting, Day rides, Audax, Incidents, etc.
Airsporter1st
Posts: 564
Joined: 8 Oct 2016, 3:14pm

Re: black ice

Postby Airsporter1st » 21 Jan 2019, 2:22pm

Every car I’ve driven which had an outside temperature warning device, alarmed at 4 degC. I assume there is good reason for choosing that figure. The problem for a cyclist is that in the manjority of cases, they don’t monitor outside temperature continuously, although that is possible with a smartphone, at least.

fastpedaller
Posts: 2072
Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: black ice

Postby fastpedaller » 21 Jan 2019, 4:43pm

Airsporter1st wrote:Every car I’ve driven which had an outside temperature warning device, alarmed at 4 degC. I assume there is good reason for choosing that figure. The problem for a cyclist is that in the manjority of cases, they don’t monitor outside temperature continuously, although that is possible with a smartphone, at least.


All (to me anyway) newer cars. Even if we had that facility, what to do... get off?

Grandad
Posts: 1040
Joined: 22 Nov 2007, 12:22am
Location: Kent

Re: black ice

Postby Grandad » 21 Jan 2019, 5:12pm

Unfortunately unless you change out the standard tyres a trike just stops you falling over sideways and not sliding onto the wrong side of the road on a bend or sliding straight through a junction.


Another problem is with ungritted roads that have had enough traffic to clear the two tracks taken by the motor vehicles. With a bit of luck 2 of the trike wheels will fit in one of these but the third one has to go on the central snow and guarantees a very bumpy ride.

One year the Birmingham-Llangollen - Birmingham 150 mile reliability trial was when an unusually heavy snowfall had thawed as far as Chirk, but the A5 after that was just 2 clear tracks in each direction. Not ideal for my trike. :( (In 1966 the A5 didn't have much traffic on a late winter Sunday)

robing
Posts: 1082
Joined: 7 Sep 2014, 9:11am

Re: black ice

Postby robing » 21 Jan 2019, 5:25pm

It's the ground temperature that is relevant to black ice formation, which can be lower than the air temperature - hence that figure.

Phileas
Posts: 192
Joined: 18 Feb 2009, 6:12pm
Location: Bristol

Re: black ice

Postby Phileas » 21 Jan 2019, 5:54pm

I believe the forecast air temperature is usually for 2m above the ground, hence the air next to the ground could be lower unless the wind keeps the air mixed.

Often, gritted roads are damp when ungritted roads are dry which confuses the issue somewhat.

Airsporter1st
Posts: 564
Joined: 8 Oct 2016, 3:14pm

Re: black ice

Postby Airsporter1st » 21 Jan 2019, 6:33pm

fastpedaller wrote:
Airsporter1st wrote:Every car I’ve driven which had an outside temperature warning device, alarmed at 4 degC. I assume there is good reason for choosing that figure. The problem for a cyclist is that in the manjority of cases, they don’t monitor outside temperature continuously, although that is possible with a smartphone, at least.


All (to me anyway) newer cars. Even if we had that facility, what to do... get off?


I think you misunderstand me - I was simply trying to answer the O.P. with a a definitive figure and then pointing out why that figure may not be valid for cyclists.

fastpedaller
Posts: 2072
Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: black ice

Postby fastpedaller » 21 Jan 2019, 6:42pm

Airsporter1st wrote:
fastpedaller wrote:
Airsporter1st wrote:Every car I’ve driven which had an outside temperature warning device, alarmed at 4 degC. I assume there is good reason for choosing that figure. The problem for a cyclist is that in the manjority of cases, they don’t monitor outside temperature continuously, although that is possible with a smartphone, at least.


All (to me anyway) newer cars. Even if we had that facility, what to do... get off?


I think you misunderstand me - I was simply trying to answer the O.P. with a a definitive figure and then pointing out why that figure may not be valid for cyclists.


My apologies if I sounded confrontational - certainly was intended to be.
I recall about 12 years ago (crikey time flies) leaving home to go to Blakeney (N Norfolk coast resort) and stop in the tea room. In the depths of the tea room, away from any windows, I had a lovely bowl of soup etc, and having paid I headed towards to door and encountered snow! On 25mm tyres and over an hour's ride I set off not knowing what I'd encounter! Luckily after heading a couple of miles inland there was no more snow on my route home.

pwa
Posts: 10240
Joined: 2 Oct 2011, 8:55pm

Re: black ice

Postby pwa » 22 Jan 2019, 9:52am

New snow is generally okay to cycle on. Cautiously.

CliveyT
Posts: 269
Joined: 13 Jun 2012, 2:55pm
Location: Cambridge

Re: black ice

Postby CliveyT » 22 Jan 2019, 10:13am

Rain overnight and then clearing up meant I went out this morning to check before setting off. Ice just crusting the tops of the puddles so I decided to go on the spiked tyres.
Back inside to swap all my work stuff into the bag for the other bike.
This bike of course was hanging furthest from the door so had to get three bikes out of the garage so I could get to it.
It only had spiked tyre on the rear so I had to swap the front wheel around
The 'spare' wheel was hanging up on the far side of the van so had to push the van out of the way to get to it (and then go to the front door of the garage to push it back in again).
This wheel hadn't been touched since I built it in July so needed pumping up.

By now the sun has come up above the hedgeline and all the ice had melte, and I didn't come across any all trip.
But at least I was safe :lol:

bogmyrtle
Posts: 895
Joined: 5 Mar 2008, 10:29pm

Re: black ice

Postby bogmyrtle » 23 Jan 2019, 7:54am

Ice can be more problematic under thawing conditions. A road can appear ok on the whole but parts that are sheltered or where the ice was thicker can be slower to thaw. Hit one of those patches when you are bowling along its virtually impossible to stay upright.
A bike does more miles to the banana than a Porsche.

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foxyrider
Posts: 4512
Joined: 29 Aug 2011, 10:25am
Location: Sheffield, South Yorkshire

Re: black ice

Postby foxyrider » 23 Jan 2019, 8:43am

bogmyrtle wrote:Ice can be more problematic under thawing conditions. A road can appear ok on the whole but parts that are sheltered or where the ice was thicker can be slower to thaw. Hit one of those patches when you are bowling along its virtually impossible to stay upright.


Pretty much what happened to me in December!
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

Scunnered
Posts: 216
Joined: 11 Apr 2014, 11:23am

Re: black ice

Postby Scunnered » 23 Jan 2019, 8:45am

MGrant74 wrote:I really don't like cycling when there is a possibility of black ice. Is there a temperature below which I shouldn't go out?

If the sky is clear of clouds then before the sun is up, black ice can form when the air temperature is +3 to +4C. The clear sky allows radiation from the ground to escape so the ground/road surface temperature can be 0C.
Another condition to be aware of is when the night starts off freezing but warmer air moves in in the early hours. The air temperature may be +3C or more but the ground remains at 0 or +1C. Black ice with a thin layer of water on top is impossible to see and slipiest of all.

fastpedaller
Posts: 2072
Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: black ice

Postby fastpedaller » 23 Jan 2019, 9:13am

fastpedaller wrote:
Airsporter1st wrote:
fastpedaller wrote:
All (to me anyway) newer cars. Even if we had that facility, what to do... get off?


I think you misunderstand me - I was simply trying to answer the O.P. with a a definitive figure and then pointing out why that figure may not be valid for cyclists.


My apologies if I sounded confrontational - certainly was intended to be.
I recall about 12 years ago (crikey time flies) leaving home to go to Blakeney (N Norfolk coast resort) and stop in the tea room. In the depths of the tea room, away from any windows, I had a lovely bowl of soup etc, and having paid I headed towards to door and encountered snow! On 25mm tyres and over an hour's ride I set off not knowing what I'd encounter! Luckily after heading a couple of miles inland there was no more snow on my route home.


I do apologise. Everyone must think I'm a real grouch! I of course meant to type "certainly WASN'T intended to be" :oops: :oops:

Airsporter1st
Posts: 564
Joined: 8 Oct 2016, 3:14pm

Re: black ice

Postby Airsporter1st » 23 Jan 2019, 1:15pm

fastpedaller wrote:
fastpedaller wrote:
Airsporter1st wrote:
I think you misunderstand me - I was simply trying to answer the O.P. with a a definitive figure and then pointing out why that figure may not be valid for cyclists.


My apologies if I sounded confrontational - certainly was intended to be.
I recall about 12 years ago (crikey time flies) leaving home to go to Blakeney (N Norfolk coast resort) and stop in the tea room. In the depths of the tea room, away from any windows, I had a lovely bowl of soup etc, and having paid I headed towards to door and encountered snow! On 25mm tyres and over an hour's ride I set off not knowing what I'd encounter! Luckily after heading a couple of miles inland there was no more snow on my route home.


I do apologise. Everyone must think I'm a real grouch! I of course meant to type "certainly WASN'T intended to be" :oops: :oops:


No apologies needed in any case and I, for one, fully understood that it was a typo first time around. :D

flatout
Posts: 19
Joined: 15 Nov 2013, 6:45pm

Re: black ice

Postby flatout » 23 Jan 2019, 4:10pm

In answer to the OP – No. And it is not the temperature at your departure time that is the criteria.

The best guide still remains the application of your own ‘common sense’ based on knowledge of your own cycling manor, habits and routes (gritted, hills and dips, water run-off, tree overhangs, urban or countryside, burst water mains, tyre selection, weight of bike and rider, overnight lows, recent rainfall, time of day, sunshine or overcast, vehicular traffic density, etc. etc.).

If in doubt leave it out.