Mecca’s population more than triples for several weeks each year during the Muslim pilgrimage. We spoke with University of Toronto professor Amer Shalaby, a transportation expert, about what the city’s response to this annual strain on its infrastructure can teach North Americans about resilience.
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How does your research on Mecca relate to the work you’ve done in Toronto?
During the pilgrimage you have mass movements of three million people who are moving from one place to another place within a window of two or three hours. If you cannot control this mass movement, it can very quickly escalate into a very dangerous situation.
The annual Muslim pilgrimage, or hajj, draws millions of people to Mecca, Saudi Arabia
There are all kinds of transportation modes that are being used to move those people. Subways are one of them, as well as buses, on foot. And there are plans to expand the public transit network to six subway lines; currently, there’s only one in operation. But all of this is not really going to be sufficient, as you can imagine. Moving three million people is such a massive problem.
I found really interesting parallels and lessons to be learned. Some of the measures that are being implemented successfully there we can perhaps copy in North America, particularly in large transit terminals where you have very heavy crowd levels.
For example, one of the projects I was involved in is evaluating the first mass rail line in Mecca. And, of course, if you leave it uncontrolled it can very easily get overwhelmed. So there’s a very thorough management system in place to dispatch crowds to that line. They stage them into the platform through a number of steps. First they dispatch groups to the line; they store them outside the station; they get them into the station from the waiting areas. There are actually two waiting areas at the platform, one in the front end of that platform and one at the back end.
So they use very smooth technology and crowd management plans which I think could be implemented in some very heavily congested transit stations in North America. It’s basically the whole concept of ramp metering, where you try to control the flow into the freeway such that you don’t overwhelm the freeway with a lot of traffic. You try to maintain a certain level of congestion on the freeway by controlling the on ramps.
The same thing with a transit station. You want to basically meter the flow into the station so that you don’t overwhelm it. It’s a well-known concept. Like, for example, during the inauguration speech of Obama there was a concern that some of the subway stations near the site could get easily overwhelmed. And some of those stations were in fact closed down. But if you have some crowd management system in place, you can basically control the inflow of crowds and passengers into the station so that you maintain the level of operation at an acceptable level.
What parallels do you see between this and current discussions about resilience?
We know from queuing theory that once your demand levels approach capacity, any small disturbance in the system can cause a very long delay. For that delay to dissipate, it takes quite a long time.
Once your demand levels approach capacity, any small disturbance in the system can cause a very long delay
So, a very simple example: When a freeway is operating at capacity and you have one lane closed down because of an incident, even if you remove that incident immediately, the queue that it results in might actually take about 10 minutes to dissipate.
This really speaks to the issue of resilience, because the definition of resiliency is the ability of a system to recover to normal operations after some disturbance occurs. So the problem now in many transit systems is that the demand levels have been outpacing growth and demand has been outpacing supply. Demand levels are in fact at or even exceeding capacity levels. So any small incident that may occur — for example, line breakdown, or even something of more minor magnitude than this — can cause huge delays.
So it becomes really very important here to identify the weakest links in the network and ask, “What can we do in order to improve the resiliency of the network by tackling those links?”
Like here in Toronto, we have a north–south subway line called the Yonge line that is operating above capacity. It carries the highest volumes of passengers of any system in Canada. If anything happens to this line, it will just bring the whole network to a halt. This really speaks to the importance of creating some redundancy, so if something happens to that link there’s some spare capacity elsewhere to absorb the delays.
Toronto subway
This hasn’t been a major issue in the past because transit demand levels haven’t been at the level of capacity, but now that many systems are at that stage you need to start thinking about resiliency quite seriously.
And are they at that stage today because of increased urbanization, or . . . ?
Well, a whole range of factors. The baby boom echo, for example. So we have the baby boomers, and then we have the baby boom bust, and then we have the baby boom echo — the children of the baby boomers. This is a big demographic that is in their late teens and early twenties and really a prime market for urban transit. Also, urbanization and rising levels of congestion and road rage are diverting a lot of people to public transit.
Traffic congestion in Toronto
So a whole range of factors really combine together resulting in rising levels of transit ridership. And we are very slow to expand our transit system to accommodate these rising levels of demand.
Interview edited and condensed.