Road gritting and snow clearance standards

Introduction

Our aim is to make Southampton’s roads as safe as possible for our road users and keep disruption caused by bad weather in winter to a minimum.

We cannot grit all the roads in the city, however, priority gritting routes have been established.

From the beginning of November to the end of March, daily weather forecasts are received and road conditions monitored to enable us to decide when precautionary salting or other treatment is required. Throughout this period a four-man crew and a supervisor are on call 24 hours a day, who can react quickly to extreme weather conditions.

Which roads are gritted and when?

We grit our roads in the order below, based on traffic flows and the best use of our gritters.

Please note that if you leave a vehicle parked on a road which is on a gritting route, you need to ensure there is at least 3 metres width remaining for the gritter to get past.

Priority One (Main traffic routes)

To be treated as routine pre-salting, in advance of any forecast of frost, ice or snow.

• Main access routes to important industrial and large educational establishments
• Main access routes to major accident and emergency hospitals, and to important emergency service locations
• Roads used as major bus routes
• Roads passing through major shopping centres
• Other routes busy during peak traffic periods
• Major pedestrian precincts and pedestrian routes following periods of extreme freezing conditions or after snowfall
• Main cycle routes/paths following periods of extreme freezing conditions or after snowfall
• Special pedestrian routes following periods of extreme freezing conditions or after snowfall
• Bridge decks and approached
• Majority of steep gradients
• Major transport interchanges

Priority Two (Other traffic routes)

To be treated only where there is prolonged and persistent frost or ice, which is expected to continue, or following snow:

• Roads near other schools
• Roads used as other bus routes
• Roads to other hospitals
• Roads to minor fire and ambulance establishments
• Roads passing through other shopping centres
• Local shopping areas
• Local footways, which link communities

Priority Three

Routes that are only attended in extreme weather conditions and on an ad-hoc basis

• Access routes to other isolated dwellings
• Residential roads
• Pedestrian precincts and busy footways
• Cycle tracks
• All other public highways
• Subway ramps and steps

Grit stocks

We normally have approximately 800 tonnes of salt stockpiled at City Depot. Under normal winter conditions a maximum of 40 tonnes of salt per day is required, so 800 tonnes is nearly three weeks’ worth of stock. In addition to this stockpile, we have access to thousands of tonnes of salt that are held by the Balfour Beatty Group. We have five gritting vehicles with GPS technology on board to monitor and audit the road gritting process

The science behind ‘gritting’

Although the process is referred to as gritting it is actually salt that is used on the road surfaces. The salt lowers the freezing point on the road surface. If the road surface is below -8°C then the salt becomes ineffective. Salt needs traffic movement to turn the salt into brine (salty water) to melt the snow; the salt will not melt the snow by itself. The roads are pre-salted at up to 15g/m² and post-salted at up to 30g/m². A decision as to whether to pre-salt is usually taken at lunchtime and the salting normally begins around 7pm after the worst of the rush hour traffic is over and well before the expected freeze. If there is an overnight snow fall following the pre-salting, then we grit again at 4am with a heavier run of around 20g/m².

The gritting routes currently cover 210 miles. Unfortunately in spite of our best efforts gritting does not always work. Heavy rain can wash the salt away. Early morning frost can be difficult to predict. It can be very hard to grit during the rush hour and ice can form before the gritting vehicles have completed their routes.

Can requests be made for roads to be gritted?

If we experience prolonged adverse weather and once the priority one and two routes are clear, we will assess and prioritise any other requests for gritting.