Double curveBelgium
Traffic rules
Belgium
261. Double curve
A double curve is a road section containing two successive curves in opposite directions. The first curve may turn left and then right, or right and then left.
The same warning sign may also indicate a longer succession of curves. Drivers should reduce speed before the first curve, remain within their lane and be prepared for the following curves to differ in direction, sharpness and length.
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Which Belgian signs warn of a double curve?
Traffic signs A1c and A1d warn of a double curve or a succession of more than two curves.
Warning for a double curve, first left then right.
Signal routier A1c • Virage dangereux. Double virage ou succession de plus de deux virages, le premier à gauche.
Verkeersbord A1c • Gevaarlijke bocht. Dubbele bocht of opeenvolging van meer dan twee bochten, de eerste naar links.
Warning for a double curve, first right then left.
Signal routier A1d • Virage dangereux. Double virage ou succession de plus de deux virages, le premier à droite.
Verkeersbord A1d • Gevaarlijke bocht. Dubbele bocht of opeenvolging van meer dan twee bochten, de eerste naar rechts.
What does Belgian sign A1c mean?
Traffic sign A1c warns of a double curve or succession of more than two curves, with the first curve turning left.
What does Belgian sign A1d mean?
Traffic sign A1d warns of a double curve or succession of more than two curves, with the first curve turning right.
Does A1c or A1d always mean exactly two curves?
No. The sign may also indicate a longer sequence containing more than two curves.
Does the sign show the direction of every curve?
No. It identifies the direction of the first curve. Drivers must remain prepared for later curves to vary in direction and sharpness.
When may Belgium install A1c or A1d?
Belgian placement rules reserve curve-warning signs for curves that appear unexpectedly or require a significant reduction in speed.
Where is the warning sign placed?
For successive curves, the sign is placed before the first curve. The placement distance is measured from the beginning of that curve.
How is the length of a winding section indicated?
A supplementary panel may display the length of the road section containing successive curves.
Can a panel indicate the distance to the first curve?
Yes. A supplementary distance panel may indicate approximately how far ahead the dangerous section begins.
Does A1c or A1d impose a speed limit?
No. The applicable regional, zonal, posted and vehicle-specific speed limits remain in force.
Must you sometimes drive below the permitted speed?
Yes. Drivers must adapt their speed to the curves, visibility, weather, traffic, road surface and condition and load of the vehicle.
Must you be able to stop within the visible distance?
Yes. Drivers must remain able to stop before a foreseeable obstruction, including one hidden beyond either curve.
When should you brake?
Reduce speed before entering the first curve. Avoid harsh braking while changing direction between the curves.
Must you remain on the right-hand side?
Yes. Drivers must normally keep as close as possible to the right and must not cut into the section intended for oncoming traffic.
May you cross a continuous centre line?
No. Drivers may not cross a continuous white line or travel to its left when it separates opposing directions of traffic.
May you overtake in a Belgian double curve?
The specified left-side overtaking is prohibited in curves when visibility is insufficient. An exception applies where overtaking can be completed without crossing the continuous white line separating opposing traffic.
Does the A1c or A1d sign automatically prohibit overtaking?
No. The prohibition depends on visibility, road markings and the ordinary Belgian overtaking rules, not solely on the warning sign.
May you stop or park in a double curve?
Stopping and parking on the carriageway are prohibited in a curve when visibility is insufficient.
May you park in a clearly visible part between the curves?
Only when all ordinary stopping and parking rules are respected and the vehicle remains clearly visible and does not create danger or obstruction.
How should you pass a cyclist?
Wait until there is sufficient visibility and space to leave at least one metre inside a built-up area or 1.5 metres outside a built-up area. Do not cross a continuous line or endanger oncoming traffic.
What should motorcyclists consider?
Motorcyclists must change lean direction between the curves while keeping both themselves and their motorcycle within the correct part of the carriageway.
What should drivers towing a trailer do?
Reduce speed before the first curve and steer smoothly. Sudden changes of direction or acceleration can cause the trailer to sway or follow an unsafe path.
What if the road is wet, icy or covered with leaves?
Reduce speed earlier and avoid abrupt braking, acceleration or steering. Grip may vary between the first and second curve.
Do A1c and A1d change priority?
No. Traffic lights, priority signs and the ordinary priority rules remain applicable at any intersection within or after the curves.
Will A1c and A1d remain under Belgium’s new road code?
Yes. From 1 June 2027, A1c and A1d retain their meanings for a double curve or succession of more than two curves, according to the direction of the first curve.
