Orkney Islands Council Winter Service Policy 2026 - 2031

Appendix 1B

CARRIAGEWAY FORECAST PERIOD – NIGHT (18:00 – 06:00)

IMAGE: Flowchart showing the night-time carriageway treatment process. A forecast received at midday leads to a decision on whether forecast road surface temperature (RST) is less than 1ºC. If not, no action is taken. If so, P1 routes are pre-treated, with treatment determined by whether the forecast is for frost/ice, snow, or freezing rain. The chart specifies dry salt application rates of 10, 20, 30, 40, and 56 g/m2 for different RST ranges, as well as 20–40 g/m2 for snow and 40 g/m2 for freezing rain. It also shows procedures for currently present ice, compacted snow or ice, and snowfall likely to be compacted by traffic.

Forecast received at Midday

Is forecast RST less than 1ºC?

• No: No action.
• Yes: Pre-Treat P1's.

Why is treatment required?

Frost/Ice

Is Ice currently present?

• Yes: Appendix 1C — Ice Procedures.
• No: What is lowest forecast RST?

Snow, Freezing rain

Before or during Snow/Freezing rain forecast?

Before

What is forecast?

• Snow: 20 – 40 g/m2 Dry salt.
• Freezing rain: 40 g/m2 Dry salt.

During

• Plough to surface if required.

Is compacted snow or ice on surface?

• No: 20 – 40 g/m2 Dry salt.
• Yes: Is traffic likely to compact subsequent snowfall before further plough possible?

Is traffic likely to compact subsequent snowfall before further plough possible?

• No: No de-icer should be spread.
• Yes: 20 – 40 g/m2 Dry salt.