Frequently asked questions

Several factors should be considered when deciding on the placement and type of passive posts, including:

• Permitted speed: The speed limit of the road will influence the required energy absorption class of the post.
• Presence of other obstacles: Consider the risk of the vehicle hitting other objects after colliding with the post.
• Presence of pedestrians: Choose a post that minimises the risk to pedestrians and other road users.
• Energy absorption rating: Select the appropriate energy absorption class (HE, LE, or NE) based on the specific location and risks.
• Sign size: Larger signs increase the wind load on the post, potentially requiring a larger section post or additional supports to ensure stability.
• Wind speed: The prevailing wind speeds in the area should be considered. Higher wind speeds necessitate stronger and more robust posts to withstand the increased forces.

Passive posts are often used in locations where traditional safety barriers are unsuitable or pose a hazard, such as:

• Roundabouts and splitter islands: Where barriers could create a greater hazard.
• Areas with limited space: Where there isn’t enough room for a barrier run-off.
• Rural roads: Where a clear “run-off” area is available beside the road.

When a road crash occurs, the vehicle and its passengers quickly decelerate, and force is exerted on the vehicle. Modern cars have safety features that absorb kinetic energy in collisions, such as seat belts, air bags and crumple zones, but this is not always enough to prevent death or serious injury to the vehicle occupants.

Colliding with a heavier stationary object such as a traditional lamp post or signpost, which is not crash-protected, could have disastrous consequences for the vehicle and its passengers. If the force on impact is not sufficient to move the object, it will send a considerable force back to the vehicle. Whereas a light object, which moves easily on impact, will absorb some of the vehicle’s kinetic energy, thereby limiting the severity of the crash.

Passive posts enhance road safety by minimising the impact forces on a vehicle during a collision. Unlike rigid posts, they break away or deform, absorbing some of the kinetic energy and reducing the risk of serious injury to vehicle occupants.

Passive signposts, also known as passive sign supports, are designed to break away or deform upon impact with a vehicle. This reduces the severity of injuries to vehicle occupants in a collision. They are often used in places where traditional safety barriers might be impractical or pose a hazard themselves or where existing sign posts cannot be moved and has to be placed within the working width of the VRS.

A guardrail is a type of Vehicle Restraint System (VRS) used alongside or on the central reserve of a road to prevent vehicles from leaving the roadway or entering hazardous areas. They are also used to protect drivers and passengers from collisions with obstacles or embankments. Guardrails are a post and rail system, typically made of metal components. 

A road restraint risk assessment procedure, or RRRAP for short, is a formal examination of a road or highway project, carried out by an independent team of experts. The audit aims to identify potential safety issues and recommend improvements to enhance safety for all road users, including drivers, cyclists, and pedestrians.

A parapet is a restrain system installed along the edge of a bridge or elevated structure where there is a vertical drop. It acts as a safety barrier to prevent vehicles from leaving the roadway and falling off the bridge. Parapets also help to protect bridge users from the wind and serve as a visual guide for drivers.