Planning in advance
We always grit the roads if ice or snow is forecast. We have our own weather station at Queens Road from where readings of the weather conditions are sent to the MetDesk every ten minutes.
Two forecasts are produced each day at 12 noon and 6pm from these readings, and we use this information to plan our gritting treatments. If there’s any uncertainty, we check with the weather forecaster. We are also alerted if there are any significant changes to the forecast at any time of the day.
Throughout the winter season, we receive a:
- two to five day forecast daily
- six to ten day outlook
This information allows gritting resources to be planned well in advance.
How we cover our roads
We have nine gritting vehicles to cover 704km of the road network across the city. It takes approximately four hours for one vehicle to treat its entire route.
Gritters are sent out to start gritting five hours before the forecast says that the road surface temperature is going to reach freezing point and that ice will form on the road surface.
In the case of snowfall or prolonged sub-zero weather conditions, the gritting fleet may be on the road continuously. It takes four to five hours to pass the same point a second time as our gritters need to go back to the depot to be refilled with salt.
When there’s heavy snowfall for more than three consecutive days, our priority is to focus on the main roads, meaning estate roads may not be treated as frequently.
How gritters work
Salt is spread from the gritter by:
- applying it on to the road beneath the vehicle
- throwing the salt to one side or both sides of the road
Salt will only be spread from the gritter once it reaches the starting point of its treatment route.
A gritter on the road may not always be gritting if it has not reached the start of the route to treat or it is heading back to the depot for a refill. If it’s safe to do so, the yellow beacon will be turned off when salt is not being spread.
Each gritting vehicle has a GPS system which tracks its route, speed, whether it is spreading salt, and the amount being spread. Checks can be made as to the date and time the vehicle was on a certain road and what it was doing.
When we can’t grit
When we have freezing rain, it is unsafe to send heavy gritting vehicles out on the roads. This is because they will have little or no traction.
Freezing rain is rare and is caused by droplets instantly freezing and coating everything in a film of ice when it lands. It covers the salt preventing it from melting the ice until the air temperature rises.
Road travel during a period of freezing rain will be severely disrupted.
Read more about gritting salt