Andrew Pettifer, Principal, and Eric Rivers, Associate Principal
As cities emerge from virus disruption and start to embrace the returning office workers, understanding the integrated nature of people movement will be key to the operators of transport systems and buildings. With social distancing and health management practices front of mind, where will the pinch points lie in our city systems and how can they be managed?
While these factors will undoubtedly have an impact on the use of mass transport, the demand for transport services are driven by where those passenger journeys lead to. For most cities of scale, the commercial office drives peak demand.
Office workers are used to the experience of arriving at peak time. Lobbies are heaving and often backed up as lift cars are fully loaded to meet the short-term peak in passenger demand. Even ‘pre COVID-19’, the capacity of a building’s lifts is usually the bottleneck in the journey up to a tenancy. As we emerge from the COVID-19 pandemic and begin to return to work, we still expect the lifts to be a major pinch point in the commuting routine, given the need to socially distance within lift cars.
So what strategies might be adopted and how resilient are lift systems to changes in demand patterns?
To explore, we’ve run a series of scenarios based on a typical mid-rise A grade building within a city. For most commercial buildings, the opportunities to make significant physical amendments to the building itself are limited. Building tenants and owners will need to consider operational and management overlays to support social distancing during reoccupation while also unlocking the choke point of the lift system.
For tenants on lower floors, they could consider the use of fire stairs for day to day access, but only for those without mobility restrictions. The goods lift could also be brought into operation for passenger movement. These measures would take demand away from the passenger lifts and necessitate increased cleaning requirements in areas not typically accessed by office workers.
Modifications to the entry lobby and tenancies could include the use of any installed Destination Control System to allocate a pre-set floor based on a user’s swipe card – removing the need to touch shared lift panels. Where installed, lifts could be called via mobile devices in a similar way that some tenants already use them to unlock doors and turnstiles – with consideration given to those who can’t use a particular technology.
For tenants with existing agile workplace strategies and/or a newly found capability to work from home, there’s the opportunity to limit occupancy through staff rostering or other methods, and to stagger arrival times of staff to further reduce the peak in lifting demand.
Building tenants and owners will need to consider operational and management overlays to support social distancing during reoccupation while also unlocking the choke point of the lift system.
But how far would demand need to be managed to adopt the practice of social distancing within a lift car itself?
Our modelling shows that for a mid-rise A grade building, a minimum 1.5m separation would mean limiting the car capacity to four people – noting that even this does not meet the Australian Government’s preferred 4m2 per person guideline. In many other smaller and older office buildings it could be two or even one person. Limiting the number of people to each car could be achieved using the Destination Control System where available, rather than relying on individual compliance.
In buildings with fewer, larger tenants, allocation of particular lifts to particular tenants/floors could assist in reducing the cross-over of people in shared cars.
Design practice for modern A grade buildings provides for a peak of 13% of occupants arriving in a five-minute period. If four passengers per lift car is the controlling factor in this scenario, a managed staggered arrival period of around two hours would be necessary to fill the building to 100% occupancy. This arrival period reduces to 70 mins and 50 mins with building occupancy of 75% and 50%, respectively.
Encouragement of a staggered arrival approach providing a specific arrival window would also reduce lobby occupancy and enable space for social distancing. Orchestration and enforcement of such a demand control regime would present significant logistical and communications challenges in large multi-tenanted buildings. It is important here to note that lift performance will likely be part of the Minimum Building Standards appended to a tenant’s Lease Agreement – so the impact of implementing such measures may need to be discussed.
Understanding how people move through spaces
The scenarios above focus on the lifting system as the bottleneck. However, when we look at how people arrive at buildings – whether by public transit, private car, walking or cycling – we need to consider that people arrive in groups influenced by the surges that come from trains, buses and traffic signals that pulse people into buildings at non-uniform rates. The result of these external influences means lobby queueing systems may need to be employed to maintain social distancing requirements while the arrival group waits for their designated lift. Our pedestrian modelling software MassMotion can help with this.
However, when we look at how people arrive at buildings...we need to consider that people arrive in groups influenced by the surges that come from trains, buses and traffic signals that pulse people into buildings at non-uniform rates.
An alternative approach is to allow lift cars to load up as normal while ensuring – as far as it is reasonably possible – that people entering the car are in good health.
In cities such as Hong Kong, lift usage is not limited but the wearing of masks is mandatory. Temperature sensing is used to check the health status of individuals entering the building – either using hand-held skin temperature devices (a fairly disruptive and slow process) or via a thermal imaging camera with further secondary screening needed using a hand-held device. The logistics of such an operation for buildings that have hundreds or even thousands of occupants is significant.
Increased cleaning measures working in tandem
Any of these interventions would need to be coupled with continued messaging around behavioural components, such as washing of hands, so as to be seen as complementary rather than supplementary. There will also be an expectation of increased, and visible, cleaning regimes. An example may be the stationing of a cleaner in the main lift lobby to periodically wipe down lift control panels and lift cars before occupants enter.
As tenants begin to journey back to work, there will be a level of acceptance of a degradation of lift performance during this period. A combination of demand management and user-led design modifications to lobby spaces could provide an important mechanism to keep our city moving while social distancing remains with us.
Adapting to a COVID-19 world
The COVID-19 pandemic is a major shock to the world. The human cost is hard to bear and our thoughts are with all those affected. As engineers, designers and consultants we have a role to play - this is a moment to be brave, try new ideas and collaborate to develop services and facilities our communities need.