How tote-based baggage handling systems optimise CBIS and CBRA screening capacity in TSA jurisdictions

There’s a reason why tote-based EDS screening lowers screening capacity at US airports but the technology can actually optimise BHS capacity overall.


Airports and airport consultants can get caught in debates about whether in-tote EDS screening lowers screening capacity and as a result can often dismiss in-tote technology.

But while tote-based EDS may technically lower capacity in the US, we explain what’s behind that. We also explain how its features can, nevertheless, actually optimise baggage handling system (BHS) capacity overall.

What is CBIS?

The screening for explosives in baggage by means of Explosive Detection System (EDS) technology has been a stable part of airport security following the Lockerbie bombing.

But EDS screening differs depending on the BHS used and where in the world it’s used.

In the conveyor-based system, loose bags travel through EDS screening on a conveyor belt. Whereas in tote-based screening, bags are placed into an individual tote before screening and stay in the tote throughout the screening.

This is how EDS screening works.

Unchecked baggage begins its security screening process by being inducted into Level 1 screening where it passes through the EDS machine and automatically checked for explosives. Cleared baggage moves to baggage makeup and alarmed baggage moves on to Level 2 screening where security officers view the image generated by the EDS machine using on-screen resolution (OSR) tools. Cleared baggage at this point moves on to baggage makeup, while alarmed bags travel to Level 3 CBRA screening for manual inspection. Bags that are cleared after Level 3 travel to baggage makeup and loaded onto planes. Some systems have the possibility to rescreen the unresolved bags that cannot be approved.

[Image source: TSA Planning Guidelines and Design Standards for Checked Baggage Inspection Systems (p. 40) ]

The process is the same whether security is governed by the TSA in America, or industry-accepted standards under ECAC, that are applied in Europe and other parts of the world that follow ECAC’s standards and approval process.

Conveyor-based viz-a-viz tote-based screening capacity

Mathematically, traditional conveyor systems under TSA testing do indeed yield a higher screening capacity but the figures are not the same when tested to industry-accepted standards under ECAC:

  • TSA: Under TSA testing, the conventional conveyor system yields a capacity of 674 bags per hour, compared to the tote-based system’s capacity of 512 bags per hour.
  • ECAC: Under ECAC, the conveyor system delivers a capacity of 1,200 bags per hour, while the tote-based system also delivers 1,200 bags per hour.

As such, there is no debate in Europe and other countries that apply ECAC standards about in-tote screening reducing capacity. There is, in fact, potential for even higher capacity as the technology improves – towards 1,400 bags per hour – which can’t be achieved on a conveyor system.

The different results between the two is that the screening machines used in the United States are slower and currently apply an algorithm with a lower threshold for detection.

It’s possible that the TSA will in its future testing reduce the fixed spacing between totes (currently 10 inches), which will increase the tote-based screening capacity. This possibility will never be available with loose baggage on conveyor belts, which is fixed at 12″.

But for the meantime we can say that in-tote screening does lower screening capacity in the US.

 However, that’s not the end of the screening capacity story.

Reducing the error rate in screening

Tote-based screening is able to reduce the error rate in screening which positively impacts the screening capacity.

Explosive detection system technology typically takes six seconds per bag to process 80 percent of the baggage, meaning 20 percent of the baggage will be sent to Level 2 screening (using OSR). Ordinarily, it takes 20 seconds to process a bag in this phase as the images of each bag is processed manually.

Of the bags arriving for CBRA, two percent will arrive from OSR because they are alarmed. An additional five percent will arrive due to an error, such as a bag that has lost its tracking during transport or has rolled in the machine curtains.

If the bag is then sent to CBRA level, it requires another four minutes to process the bag and two personnel per machine to open and manually inspect the bag, who are needed around-the-clock. In other words, two personnel are inspecting bags due to error and not explosives detection.

In-tote screening, however, can eliminate this five percent error rate and save the accompanying manpower. Because bags remain in their totes, do not roll on the belt and never lose tracking, it is only the alarmed bags (two percent) that pass on to CBRA.

Not only does the ability to deliver a reduced error rate enable OPEX savings, it also improves the screening capacity.

100 percent tracking increases capacity

One of the significant advantages of a tote-based individual carrier system (ICS) is its 100 percent tracking which means less bags will need rescreening.

Each bag is loaded into its own individual carrier at the beginning of its journey and is ‘married’ to the carrier during its entire journey through the transport and sortation system. The bag is identified by a unique radio frequency identification (RFID) tag embedded in the tote or tray.

Due to the 100 percent tracking ability, the TSA has permitted both clean and suspect bags to run on the same ICS line, saving the need for more conveyor belts and increasing screening capacity. This is not possible on a conveyor system.

A special advantage of tote-based technology such as the CrisBag integrated CBRA system is that staff don’t have to manually lift bags from one conveyor to another, eliminating manual lifting processes when dragging bags to the manual lifting table and then lifting them to the approved conveyor line. This is a huge advantage for the TSA operator.

Load sharing increases capacity

Load sharing is a unique feature that tote-based technology also offers. Balancing the load from the check-in area equally to all machines available optimises the screening equipment and avoids queues developing inside the screening system.

An ICS can actually process 3,000 bags per hour and with this overcapacity, it is easy for the BHS controls to share or balance the load between different machines. For bigger ICS systems, all the screening machines can be concentrated in one place, to which all bags are run.

Conversely, in a conveyor system, balancing is not possible. There is therefore a tendency in the conveyor system to spread machines around the system, which can cause inefficiencies if just one screening machine is being used to process a pile of bags.

Load sharing can increase capacity because it increases the utilisation of the screening machines. But it also helps to maintain the lifespan of the screening machines. No machine remains idle while others are overused; all are used to balance the load equally.

Other advantages of in-tote systems

Finally, it must be remembered that in-tote systems have many features.

Firstly, the entire screening matrix consumes much less footprint than conveyor systems – a factor very important to brownfield sites. Because ICS can handle double the capacity of conveyors, adding extra conveyor feeds to cope with capacity is not necessary. What’s more, suspect bags do not require extra lines but can be merged on the same line as cleared bags. Here, the airports can make significant costs both in terms of space and equipment.

Then there’s the manpower savings that tote-based screening offers. The TSA’s current Planning Guidelines and Design Standards for Checked Baggage Inspection Systems – which approves ICS as meeting its security requirements –  notes that:

“ICS is most beneficial in the centralised screening operational design where EDS and CBRA  staff could be minimised without compromising time-in-system constraints.”

Lastly, tote-based systems provide higher redundancy than conventional systems, allowing for easy diversions and merges on lines that carry empty totes back. And these empty tote lines do not need to mirror the entire system.

It was for these reasons – and the fact that ICS consumes considerably less power than traditional conveyor systems – that San Francisco International Airport decided to implement tote-based technology at its Harvey Milk terminal. Five independent baggage handling systems and 15 CTX machines have been consolidated into one centralised screening matrix with just seven screening machines now needed for baggage screening within the terminal.


A tote-based system might lower the peak capacity of the individual screening machine at first glance. However, the explanation for this is technical, including slower screening machines and tote lengths. But that being the case does not undermine the clear advantages offered by in-tote systems – the 100 percent tracking, reduced error rates and load sharing. In fact, with a cleverly designed, centralised tote-based screening matrix, the decidedly better utilisation of the system often lowers the amount of screening machines needed.

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