Jamie Watson and Ian Buchanan of Edinburgh Road Services explain how Edinburgh moved past 'one forecast fits all' and saved 22% in costs.
For many years, Edinburgh used a 'one forecast fits all' approach to de-icing during winter conditions. If freezing was expected, city teams laboriously salted all 650km of the city’s priority road network. These full-city 'pre-grits' usually require a great deal of labour, cause 'knock on' operational disruption, and eat away at the budget.
Today, with consulting and technology from partner Vaisala, and by using three-domain forecasting, winter weather decision managers now only treat the roads that need treating.
The results are already in. Last year, Edinburgh did a pre-grit on 39 occasions, many of which required only partial coverage on the road network. Compared to the old all-or-nothing approach, this saved the city 22% in costs, not to mention environmental savings from reduced truck mileage and salt use.
Localized forecasting, city-wide savings
The Vaisala partnership began with thermal mapping of the entire Edinburgh area over the winter of 2017-18, which identified the most important variations in elevation, road temperature, and typical salting needs.
Edinburgh’s winter weather team had an intuitive understanding of these variations, and the outputs from Vaisala’s thermal mapping aligned with them.
However managers did not have the data and science to make decisions just based on intuition. Vaisala provided that, and the partnership has resulted in several key changes:
- The city is now broken into three domains: 1) City centre and north coastal, 2) South upland, and 3) West coastal/rural. (pictured above)
- Each domain receives a separate weather forecast of road conditions from an existing forecast contractor, which is validated in real-time by a Vaisala weather station installed in each area.
- Three separate treatment decisions are made each night during the winter. Sometimes treatment is applied to all domains; sometimes it is only necessary in one or two. The financial savings from the first winter of use (2018-19) have already paid for the thermal mapping exercise.
To take advantage of the savings, the city’s winter weather team had to update their routes and improve their internal processes along the way. For example, they adjusted their routes so each of the three domains was more or less self-contained, eliminating inefficient route overlaps. They also digitized maps that had originally been drawn up on paper — an important modernization.
The city’s team also say the system is well-suited to Edinburgh’s moderate climate, where wintry weather often straddles the line between freezing and not freezing. They appreciate having the science and real-time data to make the right decisions to keep Edinburgh moving safely, while not wasting money and needlessly impacting the environment.
This new approach isn’t just about saving taxpayer money, though this is an obvious benefit. Less salt strewn across roadways means less runoff and contamination of waterways, as well as less wear and tear on vehicles; these environmental impacts are very important to Edinburgh and the wider community. The efficient use of available resources also allows Edinburgh to maintain its level of winter weather service rather than having to make cuts.
Future weather patterns will show just how drastic these improvements are in the long-term, but with winters looking to be warmer and wetter, there are likely to be more occasions when the temperature is hovering around freezing — thus more opportunities to save. For now, the 22% financial savings and notable improvements to systems and efficiency have validated the initiative for all concerned.