1. What is a gap?

A gap is an opening in the central reservation crash barrier which is located on dual carriageways that provides a point where in special circumstances vehicles may cross over from one carriageway to the other. For example the gap may benefit emergency vehicles or providing a traffic contra-flow when major accidents or maintenance works take place.

2. What are the risks of leaving a gap permanently open?

The gap provides an un-protected cross over point where a vehicle could cross over into the path of an approaching vehicle on the adjoining carriageway with horrific accident consequences.

3. What is an opening gap?

A high containment vehicle restraint system placed between the ends of existing crash barriers which can be partially or totally opened in a few minutes.

4. What properties must an opening gap have?

It must withstand impacts from buses which are the fastest heavy goods vehicles travelling on motorways.
It must withstand a small car impact so that the occupants will not suffer from high-ASI- acceleration / deceleration levels and the passenger compartment is minimally damaged.
It must have a suitable working width - deflection - so that it can fit into the available central reservation width, even where it is particularly narrow.

5. What are the design features of the S-A-B^® opening barrier?

S-A-B^® has been designed to work with most of the vehicle restraint systems which meet the EU Standard EN1317
It meets the requirements of ENV 1317-4 :
ú at the H2 –bus- level when the unit buckled by about 1m without causing serious damage to the bus which was driven away from the crash site without any external help.
ú at the TB11 –900 kg car- level when an ASI level of 1 (class A) was recorded and no car windows shattered.

6. What are the ideal requisites for an opening gap?

Service personnel should be able to open the gap in just a few minutes so that an emergency situation can be quickly responded to.
Two types of openings should be allowed for ;
ú emergency opening say 4 m wide
ú traffic diversion to allow contra-flow two or four lanes wide

7. How does the S-A-B^® barrier open?

The S-A-B^® module units have wheels which are lowered by their screw cranks to the ground. The module units have connecting hinge pins and posts which can be removed depending on how many module units are to be opened.
Emergency passage can be obtained by removing a module and moving it one side.
The entire unit may be opened by lowering the wheels and removing the central hinge pins and pushing the modules to one side. The action is similar to that required to open a gate.
Time taken to do this is between 5 and 10 minutes and no special tools are needed.

8. Why is the point between the opening gap unit and the existing fixed crash barrier so important?

The space or gap at this point must not be too wide and the correct fittings and connections must be made so that vehicles will not be caught (or pocketed) up in it. A head on crash impact against the end of the fixed crash barrier could cause a horrific accident if the gap is too wide.

9. What is the connection between the S-A-B^® and the fixed crash barrier made?

The S-A-B^® opening barrier is provided with special couplings which are designed to be fixed to the adjoining crash barrier. These couplings are designed to withstand crash impacts and to suit the form of the adjoining crash barrier which may be in steel or concrete construction.

10. How is the S-A-B^® opening barrier supplied?

The package is made up of pre-assembled 4,3 m long steel modules, 2 anchorage units with posts and couplings to suit the adjoining crash barrier.

11. How is the S-A-B^® opening barrier installed and how long does it take?

Installation instructions describe the procedures and equipment required. Installation will take account of the site specific Health & Safety plan including arrangements for traffic management.
A pre-formed hard surface is required so that the wheels have a smooth path when the barrier is opened or closed.
The installation equipment needs to include :

• Post driver for the cable anchorage posts
• Lorry mounted crane
• Small tools –shovels, spanners ,sweeping brushes etc.
• Plus 3 trained personnel

The time taken is usually four hours including the time to make the couplings to the adjoining side crash barrier but this excludes the time to put up and take down the traffic management system or to form the hard surface or take out existing barriers to form the opening.

12. What maintenance is required for the S-A-B^® opening barrier?

Maintenance instructions describe the procedures and equipment required .An annual inspection is recommended including the cleaning and protection measures so that excessive amounts of dirt and rubbish do not build up particularly at the hinged joints which will assure best performance when regularly lubricated.

13. How is the S-A-B^® opening barrier repaired after a crash and how long does it?

Repair instructions describe the procedures and equipment required which will take account of the site specific Health & Safety plan including arrangements for traffic management.
The work usually involves :