Orkney Islands Council Winter Service Policy 2026 - 2031
Appendix 1A
CARRIAGEWAY FORECAST PERIOD – DAY (06:00 – 18:00)
IMAGE: Flowchart showing winter carriageway treatment decisions following receipt of a forecast. It distinguishes between forecast road surface temperatures (RST) of less than 1°C and 1°C or above, current or forecast ice, snow and freezing rain, rain before freezing, and whether snow or ice is compacted. Treatment rates range from 10 g/m2 to 56 g/m2 of dry salt according to the lowest forecast RST and conditions.
Forecast received
Is forecast RST less than 1°C?
- No: No action.
- Yes: Is Ice, Snow or Freezing rain currently present?
Ice, snow or freezing rain currently present
Yes: Treat P1's. Then P2's if conditions continue, then P3's (Snow clearance only) where snow has been present for more than 24 hours and is likely to prevent access.
No: Is Snow/Freezing Rain Forecast?
Yes: What is forecast?
Freezing Rain: Treat P1's. Then P2's if conditions continue. 40 g/m2 dry salt.
Snow: Treat P1's. Then P2's if conditions continue. 20 – 40 g/m2 dry salt.
No: Is rain forecast before freezing?
Yes: Assemble crews and treat P1's AFTER rain stops.
No: No rain, Rain forecast during freezing. Treat P1's, then P2's if conditions continue.
Lowest forecast RST
| Lowest forecast RST | Treatment |
|---|---|
| 1°C to -2°C | 10 g/m2 dry salt |
| -2.1°C to -4°C | 20 g/m2 dry salt |
| -4.1°C to -7°C | 30 g/m2 dry salt |
| -7.1°C to -10°C | 40 g/m2 dry salt |
| Below -10°C | 56 g/m2 dry salt |
Ice, snow or freezing rain currently present
What is present?
Snow, Freezing Rain: Plough to surface if required.
Is compacted snow or ice on surface?
Yes: Is traffic likely to compact subsequent snowfall before further plough possible?
Yes: 20 – 40 g/m2 dry salt.
No: No de-icer should be spread.
No: 20 – 40 g/m2 dry salt.
Ice: Appendix 1C Ice procedures.