SlopeIreland
Traffic rules
Ireland
12. Slope
A slope is a section of road that rises or descends noticeably. A steep slope can affect vehicle speed, braking distance, traction, visibility and the ability of heavy or low-powered vehicles to maintain a steady speed.
Warning signs may indicate a steep ascent or dangerous descent and may show the gradient as a percentage. Drivers should adjust their speed early, select a suitable gear and remain prepared for slow vehicles, bends and changing road conditions.
Wikimedia.org • Kenneth Allen • CC BY-SA
What is a road slope?
A road slope is a section of road that rises or descends over a particular distance. It may also be called a gradient, incline or decline.
How can you recognise a steep slope?
A steep slope may be indicated by a warning sign showing an ascending or descending road. The sign may also display the gradient as a percentage.
What does a gradient of 10% mean?
A gradient of 10% means that the road rises or falls approximately 10 metres for every 100 metres travelled horizontally. It does not mean that the road is inclined at 10 degrees.
What is the difference between an ascent and a descent?
An ascent rises in the direction of travel, while a descent falls in the direction of travel. The same section of road is therefore an ascent in one direction and a descent in the other.
Does a slope warning sign impose a speed limit?
Not normally. It warns of a hazard rather than setting a numerical limit. Drivers must still respect the applicable speed limit and reduce their speed further when necessary.
How should you approach a steep descent?
Reduce speed before the descent, select a suitable gear and maintain a safe following distance. Avoid allowing the vehicle to gain excessive speed.
Which gear should you use when descending?
Use a gear that provides sufficient engine braking and helps keep the vehicle at a controlled speed. The appropriate gear depends on the vehicle, gradient and road conditions.
Should you coast downhill in neutral?
No. Coasting reduces engine braking and may make it harder to control the vehicle’s speed. Keep the transmission engaged while descending.
Why should you avoid continuous heavy braking?
Continuous braking on a long descent can cause the brakes to become excessively hot and lose effectiveness. Select a suitable gear, control speed early and use the brakes progressively when needed.
What is brake fade?
Brake fade is a reduction in braking performance caused by excessive heat. It can occur when the brakes are used continuously during a long or steep descent.
How should you drive uphill?
Select a suitable gear before the engine begins to struggle and maintain a steady speed where possible. Be prepared for heavy or low-powered vehicles travelling slowly ahead.
May a vehicle lose speed on a steep ascent?
Yes. Heavy vehicles, vehicles towing trailers and low-powered vehicles may slow considerably. Other drivers should maintain a safe distance and avoid impatient manoeuvres.
May you overtake near the top of a slope?
Do not overtake when the crest prevents you from seeing far enough ahead. Overtaking near a hilltop may also be expressly prohibited by local law, signs or road markings.
Why is visibility limited near the crest of a slope?
The road surface itself may hide approaching traffic, stopped vehicles, pedestrians or other hazards beyond the crest.
Who has priority on a narrow slope?
Some countries give priority to uphill traffic, while others rely on signs or ordinary obstruction rules. Drivers must follow local law and cooperate when passing is difficult.
How should you meet another vehicle on a narrow slope?
Reduce speed and use a passing place where available. The driver who can reverse or move aside more safely should cooperate, subject to any applicable priority signs or local rules.
How do rain, snow or ice affect a slope?
They reduce traction and make acceleration, braking and steering more difficult. Increase the following distance, use smooth controls and reduce speed before entering the slope.
Why are cyclists vulnerable on slopes?
Cyclists may travel slowly and move less steadily when climbing, while they may reach high speeds when descending. Drivers should leave sufficient space and avoid overtaking without a clear view.
How should you park on a slope?
Use the parking brake, select the appropriate gear or parking position and follow local rules concerning wheel position. Make sure the vehicle cannot roll into traffic.
Can a slope affect towing?
Yes. A trailer increases the load on the engine and brakes and may affect stability. Drivers should use a suitable gear, maintain additional distance and avoid excessive speed.
