When events are planned with large crowds in space accessible by vehicles, the thinking behind planning for such events now has to change. In a city where many facilities were designed in times where the population was set at 1–2 million we are now confronted with a wider Greater Melbourne population base of over 5 million, including nearby provincial cities such as Geelong and the Mornington Peninsular. The simple fact is that within such a population base there will be those that are seriously unbalanced or unhinged mentally as has been demonstrated with both the Bourke St rampage and the Flinders St incident.
It’s time in many instances to provide permanent Hostile Vehicle Mitigation systems to protect areas such as Transport Hubs, Pedestrian Malls and Sporting Facilities.
But in other instances, such as Street Festivals, outdoor markets and peaceful demonstrations, it is now necessary to provide portable units that can be installed quickly, cost effectively and removed upon the event or function finishing.
The Meridian Crash Barrier system will stop a hostile vehicle completely even up to 50km/h!
The Federal Government has developed a security strategy to prevent such vehicular attacks and we continue our reprints on the working paper created.
Vehicle Security Barriers (VSBs)
VSBs can be passive (static) or active (functioning/ mechanical) in their operation. Active devices are susceptible to mechanical failures and human error/ deception techniques, and require maintenance and ongoing costs; accordingly, passive barriers are preferred when there is no operational requirement to provide vehicle access into an area.
When selecting a barrier the foundation and installation is just as important to consider as the barrier itself. Poorly designed foundations can compromise the performance of a barrier in resisting high-energy hostile vehicle impacts.
Manufacturers offering an impact-tested VSB should also be able to offer a tested and approved foundation design for that product. Other considerations when installing a VSB include:
- The presence of underground obstructions
- Ground conditions
- The perceived calculated impact loading
- Protection to underground services in close proximity
There are a great number of options for creating effective passive barriers around an asset. They need not be costly to install and can easily fulfil aesthetic requirements of the space and its patrons, as well as the requirements of HVM.
A balance should be struck between proportionate security measures, the needs of the local businesses and functionality of public space. It is possible to integrate bespoke HVM measures into most public realm features.
Urban elements that can be used include:
- Landscape features (e.g. sculpted or clad earthworks, steep verges)
- Shrouded bollards (i.e. designed to match local architecture)
- Decorative, structural or energy absorbing planters (i.e. more aesthetically acceptable)
- Strengthened ‘light’ structures (e.g. bus or smoking shelter, information sign)
- Large immovable landmarks (e.g. statues, walls)
- Integrated street furniture (e.g. lighting column, traffic signal, seating, cycle rack)
- Level changes (e.g. steps, high kerbs)
- Water features (e.g. fountain, pond or pool)
Defining vehicle and pedestrian spaces
Designing and protecting pedestrian-only areas around assets is essential not only to protect pedestrians who would ordinarily use the space, but has the added benefit of restricting vehicle access to the buildings, creating standoff and natural barriers.
The best way to protect pedestrians is to create clearly defined pathways separate from vehicles. This can be achieved through the use of barriers along the edge of footpaths or by integrating walkways into new developments that limit vehicle accessibility but maintain easy access for pedestrians ensuring their safety. Designs like these may also help reduce the opportunity for accidental collisions between pedestrians and cars, which are quite common in carparks.
There are various designs that can help to define and reinforce pedestrian areas but should not be relied upon as the sole source of protection. These can include:
- Raised footpath
- Cobbles near gutter
- Lights on the ground (car parks)
- Verge; and
- Medium strip
Stairs will stop most but not all vehicles and can be used to add a level of protection to high-pedestrian areas or gathering points. Their main use is in mitigating out of control vehicles, or slowing down determined vehicles; they may also act as a visual deterrent (target hardening). However, they should not be solely relied upon to protect critical infrastructure, since some vehicles (short wheel base and high front end) can easily mount stairs.
The images to the left show Civic Pavilion precinct in Sydney which incorporates a combination of stairs, a sculptured garden structure, and bollards to separate the pedestrian space from vehicles.
Access for emergency and maintenance vehicles into the space is managed through the use of removable bollards.
The venue provides a good example of how effective but subtle vehicle mitigation options can be integrated into the design, establishing a pedestrian environment safe from the risk of hostile vehicles.
Separating vehicle and pedestrian spaces can be achieved by strategically placing vehicle security barriers to define those spaces. Installing metal bollards on the edge of the roadway, in the image below, provides protection for pedestrians against a vehicle attack.
The large pedestrian space between the building and roadway creates additional stand-off distance that significantly reduces the building’s vulnerability to a vehicle-borne improvised explosive device (VBIED).
The option of seating as a mitigation device at this location would not be appropriate, since the absence of a raised gutter between the roadway and pedestrian pavement increases the risk of injury to pedestrians in the event of a vehicle impact.
In designing pedestrian only spaces, consideration must be given to the volume of people (including wheelchairs and prams) movement in and out of a venue, together with access to the space by emergency and maintenance vehicles. This coupled with a comprehensive vehicle dynamics assessment should influence the shape and style of appropriate vehicle security barriers.
Sculpture and street
Riverside upgrade: sculptured feature
Riverside upgrade: sculptured feature
Suitable space for passive barriers
Steps on a pedestrian street
- For effective barrier placement the maximum clearance between two barriers should be no wider than 1200mm
- The barriers should also have a minimum height of 500mm
There may be naturally formed barriers located around a site that could be used as part of a secure perimeter. Natural barriers could include rivers, ponds, lakes, densely wooded areas, steep slopes or changes in ground level that will either divert attack or preclude vehicle passage.
Where these features do not naturally occur it may be feasible to engineer them. In these cases, consideration must be given to access and egress paths for pedestrians and general crowd management around the venue or asset.
The recommended solutions are to construct a ditch, bund or combination of the two. Considerations such as cost (and long-term cost benefit), availability of materials/production facilities, ground conditions and architectural advantage will influence the choice of options.
Trees and fences
The use of individual trees as a VSB is not generally recommended. This is because full-scale impact testing of trees has indicated that trees do not necessarily perform well against a determined hostile vehicle impact.
Where an existing tree cannot be moved and forms part of the physical perimeter, a number of factors should be considered:
- Tree health
- Stability of local ground conditions around the tree roots
- Trimming of branches to remove climbing aids (e.g. over a perimeter fence); and
- Lines of sight for guard-forces and CCTV surveillance.
Where areas of bush, forest or other densely packed trees are present to form a natural barrier, the combined resistance will likely be more effective against determined vehicular impact. In this instance, any gaps between trees may only require lower grade infill HVM measures to prevent a slow speed encroachment attack.
Most conventional fences are not a viable option for a HVM measure; they are easily breached by vehicles at low speeds and should only be used where vehicle speed is restricted by terrain or
approach. Fences are better suited to assist perimeter monitoring by installing perimeter intruder detection systems (PIDS) like motion sensors on the fences.
If vehicle access to the asset is required, then active barriers can be used to identify and monitor vehicles allowed past the standoff perimeter.
Use of an active VSB is required for control of vehicle access. The term “active” refers to the system’s ability to operate from closed (secure) to open, and could take a number of forms, such as:
- Retractable bollard;
- Retractable blocker; and
- Folding, sliding, swinging, rising-arm gate.
Retractable bollard and rising-arm gate
An active VSB can be manually operated by a person or powered (e.g. hydraulic power source). A VSB should be selected not only on the basis of performance or operational requirements, but also
cost. Careful consideration should be made by the consultant and purchaser as to the full cost of a VSB, especially post-installation costs and long-term requirements such as:
- Service requirements;
- Maintenance and repairs;
- Spare parts;
- Environment e.g. salt corrosion;
- Positioning of controls e.g. ensure they are secure; and not accessible by the public;
- Drainage issues.
If an active VSB is required then a well-designed vehicle access control point should ensure that guards are not put under undue pressure or distracted by traffic management requirements that
might prevent their being able to carry out security procedures safely and securely.
Vehicle access control point
The ideal VACP deploys two rows of VSB at the end of a VSB enforced chicane. One row at the start and another at the end of a VSB enforced chicane as per diagram. This creates a contained secure zone that a vehicle cannot enter or leave until authorised by the guard forces or an automatic access control system. This type of VACP uses up a lot of land space and is expensive to install and maintain; thus, while ideal, this type of VACP is only suitable to certain areas.
Imperative to control points are rejection lanes, search bays or parking facilities that have not been illustrated in this diagram.
Standards for vehicle security barriers
International Standards Organisation (ISO), International Workshop Agreement (IWA) 14-1 & 14-2. 2013.
Part 1 relates to the performance requirement, impact test method and performance rating.
IWA 14 -2 :2013
Part 2 relates to the application of vehicle security barriers.
The selection and installation of vehicle security barriers must include consideration of relevant legislation and general crowd management. For example; public access and safety, accessibility for wheelchairs and prams.
AML Risk Management can provide both the planning, expertise and installation of the Meridian Crash Barrier system as is required, as well as timely removal upon completion of any event.
Remember AML Risk Management for Planning, Prevention and Protection. It’s the right choice.