Speed Up or Spread Out? by CrowdVision’s Co-Founder, Fiona Strens

Should I turn my head away? Should I speed up or slow down?” Familiar thoughts for many of us as we get used to living in a world of social and physical distancing. We spend our days assuming that anyone, outside our trusted bubble, could be a COVID-carrier. In every environment beyond our locked-down homes we wonder whether that place is safe to venture into:

  • Have the managers planned and designed for safe separation? Is there evidence of them limiting the number of people allowed into each confined space? Are there signs and stickers and announcements to explain the plan?
  • Are the staff monitoring and managing the space proactively to maintain safe separation? Are there staff and technology interventions to keep people apart?

If only that was all we had to think about! In fact, we know that the risk of disease transmission is not one dimensional. It is not just about keeping apart but also about minimizing the amount of time we are exposed to close-by people. It has two dimensions.

Risk = f (Separation, Exposure)

This means that if we glide past someone quickly, it probably doesn’t matter. But if we face each other and chat for 20 minutes, we may indeed have a problem, even if modestly separated. For any interaction between two people there is a resulting disease transmission risk that can be viewed on a grid like this.

This concept is very well explored in a Wall Street Journal article which focuses on analyzing risk in stadiums but has relevance in any crowded location: https://www.wsj.com/articles/as-covid-19-closes-stadiums-municipalities-struggle-with-billions-in-debt-11591263000

How close is too close? How long is too long?

Is Exposure (time) more important than Separation (distance) or vice versa? How close is too close? How long is too long? These are questions that have no single answer.

Depending on the disease we’re running from, how it spreads, the prevalence in the near-by population, the characteristics of the environment and even personal risk profiles and tolerances, we will need to change how we define “too close” and “too long” by creating thresholds on our grid as shown here.

This shifting risk map – as thresholds are adjusted – is important because it means the same interaction between two people represents different levels of disease transmission risk in different scenarios. Look below at how the black dots, each representing a risky interaction between two people, deliver different risk outcomes depending on where the acceptable Separation and Exposure thresholds are set.

Speed Up or Spread Out?

Using analysis tools like this to assess risk to people as they pass through specific locations at specific times enables the managers of busy venues to understand where and when and why risk is high. Is it because people are too close together, exposed to each other for too long or a combination of both? Depending on this analysis, interventions can be made to either “spread people out” or “speed things up.”

Spreading People Out in Airports

This generic theory can be applied to great effect in airports. Here are some practical interventions to spread people out:

  • Limit Passenger Volumes: Control the number of people allowed into confined spaces so that they can in theory be safely separated, given available floor area. This may be done by keeping people in (separation-enforced) overflow queues until there is capacity. Or by implementing virtual queueing or other appointment-based arrival flow management strategies.
  • Redesign Layouts: Put effort into planning passenger flows and laying out queuing, servicing, waiting and seating zones to ensure both passengers and staff can safely separate.
  • Resource Smartly: Allocate assets, such as security lanes and check-in desks, and accompanying staff in such a way as to spread activity out to ensure both passengers and staff can safely separate.
  • Intervene in Real-Time: When people are getting too close, take action to spread them out. This might be by directing customer service staff to crowded locations.
  • Empower Passengers to Self-Separate: When people are getting too close, communicate with them to encourage them to self-separate. This might be by using announcements or messaging via screens, apps or notifications.

Speeding People Up in Airports

Here are some of the interventions that can be made to speed passengers through the most risky (crowded) parts of their airport journey:

  • Move Processes Offsite: Mandate or encourage processes, such as health screening, check-in, bag drop and possibly even security screening to be carried out offsite to limit the amount of time and engagement needed in the airport.
  • Streamline Journeys: Consider options to change passenger and staff routes to get people as directly as possible through their airport journeys. Coordinate across the length of the journey so that passengers don’t speed through one segment, only to hit congestion later.
  • Resource Up to Cope with Passenger Volumes: If check-in zones, security checkpoints and immigration operations are optimally resourced, there will be the right numbers of staff, desks, kiosks and lanes to avoid the build-up of queues and to speed passengers on their way.

Many of these options are included in the latest guidance from the ICAO CART (Aviation Recovery Task Force):  https://www.icao.int/covid/cart/Pages/Airports-Module.aspx. In many cases, the goal will be both to spread people out and speed them up. These goals are not in conflict but do present complexity and will require effective modelling and planning, excellent use of data, and user-friendly tools to support the decision-making processes in real-time and over-time.

At CrowdVision, building on our 10-year history of measuring crowd dynamics and keeping people safe in crowded places, we have put a lot of thought into our new SafeDistance product.

The SafeDistance product has not been designed in isolation. Our customer-partners in locations like Miami International Airport and JFK T4 have co-developed the use cases and shaped the product. It’s here, it’s now and if you are interested please contact us at safedistance@crowdvision.com

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