What Is the Difference Between a Sealed and Unsealed Road?

Sealed roads are the carriageways we normally drive upon, including motorways, residential streets, A roads, industrial estates, and parking areas. They are designed and built to varied standards to improve driver safety and provide a smooth, durable, and weather-resistant surface. Unsealed roads are those that haven’t been sealed with emulsions or other surfacing materials.

Examples include country lanes, unpaved access routes and private driveways or forestry trails. Other instances where an unsealed road might be present include beaches, tracks, fields, and off-road scenarios.

Safety risks and maintenance requirements are considerably different between sealed and unsealed roads. In some cases, an unsealed road may be assessed as unfit for purpose if presented as a viable access route for high traffic volumes, public right of way, or a route for HGVs.

Why Are Unsealed Roads Dangerous for Drivers?

The nature of an unsealed road means that the driving conditions may change with little warning. Unlike a conventional highway, the road surface could be gravel, mud, or grass instead of asphalt, bitumen, or concrete (although tarmac/asphalt is the primary surfacing material in the UK).

Highways contractors engineer road surfacing with a system of sublayers, each ensuring that the top layer is tough, long-lasting, and won’t suddenly develop cracks, deviations, or potholes.

Potential dangers of driving on unsealed roads can become very serious:

• Vehicles are likely to overturn or flip if they hit an uneven surface at speed or when travelling around a corner.
• The absence of road markings and signage can make monitoring or controlling driver behaviours difficult, particularly where an unsealed road adjoins a sealed carriageway, junction, or roundabout.
• Unsealed roads do not have any safety additives incorporated in modern highway design and can have little or no friction and long stopping distances.

The potential for accidents and collisions is considerably higher on unsealed roads, and the outcomes of accidents are likely to be more severe.

Standing water can accumulate on the surface of unsealed roads, causing further deterioration, concealing large cracks or holes in the road surface, and leading to skidding and aquaplaning, where the driver loses control of the vehicle.

Safety Requirements for Unsealed Roads

There are some circumstances where an unsealed road can be used as a designated access route, such as for a temporary workplace or ongoing development site. Managers remain responsible for implementing basic safety standards.

Even if an unsealed road is considered suitable, it is expected to meet the same requirements as sealed highways.

Site managers and planners should assess the types of vehicles that will use the unsealed road, for how long, and for what purpose. If the project is over a longer timeframe, they will likely be required to carry out maintenance or preparatory work before the roadway can be used safely.

Driver competence and safe working systems come into play. Managers need to consider how they will control traffic flows, inform drivers of the conditions, and supervise road usage and the state of the surface.

Important Maintenance Tasks for Unsealed Roads

Route planning is important, and some of the maintenance tasks necessary may include:

• Draining surface water and standing water from the road surface. Leaving water in situ can cause the roadway to worsen, so digging natural drainage ditches can be a solution.
• Slopes on the side of the road cannot be too steep to contradict safety standards. Longer sloping routes can be adjusted to introduce a varying slope instead of a continuous gradient because this prevents surface water.
• Safe work systems might include temporary road signage and traffic lights.

Some routes will require safety banks, which prevent vehicles from falling over steep edges. Banks can also be used to direct traffic along the correct path. Banks should be at least 1.5 metres in height or meet the axle height of the tallest vehicle that may be likely to use the unsealed road – whichever is higher.

Safety banks must also be robust enough to withstand a vehicle collision and can be constructed from concrete safety barriers and other assets.

Maintaining a Sealed Road

Highways planners, local governments and transport system supervisors are responsible for assessing the road networks across the UK. These assessments look at the surface bitumen and the sublayers of the road to evaluate whether repairs are required.

Cracking, deviations, aggregate stripping away from the surface, a deterioration of the bitumen binder and potholes are indications that maintenance is necessary.

Roadway repairs vary and can involve seal renewal or resurfacing, renewing the asphalt surface, or replacing the layers where a repair is impossible.

Maintaining an Unsealed Road

Responsibility for the maintenance and upkeep of an unsealed road will depend on the location of the route, how it is used, and by whom.

If the unsealed road is used as a public access route, the regulatory requirements to ensure safe driving conditions are met are likely to be more rigorous. 

Unsealed roads require more frequent inspections and detailed risk assessments, with work needed periodically to ensure the road surface is smooth enough and without large deviations that are likely to cause an increased risk of accidents.

On private land, such as farm tracks inaccessible to visitors or the public, an unsealed road may be the landowner’s responsibility, and they may be able to maintain the route at their discretion if it is only available for their personal use.

However, insurance is often invalid when driving on unsealed roads, and some drivers, hauliers, couriers and rental vehicle providers will not cover accidents or damage incurred.

Sealing an Unsealed Road

Unmade roads can be sealed and upgraded using a range of surfacing materials, protecting the surface from further degradation, installing a robust, durable sublayer, and ensuring the road is compliant with safety standards around safety banks, edging, draining and anti-skid performance.

Reactive road repair materials are designed to respond to apparent maintenance issues, such as ruts. In contrast, preventative services can preserve and protect the roadway surface and avoid deterioration before the maximum lifespan of the road.

Once an unsealed road has been repaired or replaced, preventative measures can be an optimal road surfacing solution and ensure the route remains safe, in good condition, and compliant for ongoing use.