Sensors tally taxi coverage, not fares

MIT researchers analyzed traffic data from nine major cities. (Getty Images)

In the grand world of technology, it’s a well-known fact that sensors can do just about anything. More exactly, there is a sensor available for every parameter that one would ever need to measure.

A major area of development, one that was featured quite extensively at Sensors Expo 2018 and will likely be of great interest at Sensors Expo 2019, is air quality measurement. Air pollution and climate change are the driving forces behind this increasing concern for air-quality measurement.

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Measuring air quality and/or detecting specific pollutants and gases in the static environment is a fairly simple process. Take the heavily travelled streets of a city like Manhattan for example. Researchers can attach various types of air sensors to standing light posts, signs, buildings, and other static structures to measure myriad elements in the air 24/7.

This approach covers one basic parameter: what is the air quality of a given area at various times during the day. For some studies, that may be all the researcher needs. However, if the source of air-quality change is mobile and knowing how much ground the source is covering while impacting the environment is necessary, then a slightly more involved solution is required.

For example, an MIT-based team of researchers posed a hypothetical situation. “Suppose you have 10 taxis in Manhattan. What portion of the borough’s streets do they cover in a typical day”? Obviously, in this case, sensors cannot be stationary as mentioned earlier. The simple solution would be to attach wireless sensors to the taxicabs. These components have become inexpensive, so a great number of devices can be deployed.

How far is the reach?

To find out what portion of a borough’s streets the cabs cover in a typical day, the MIT researchers analyzed traffic data from nine major cities on three continents. They found that a few taxis can cover a large amount of ground, but it takes a lot more to cover a city comprehensively.

To clarify, let’s use this example. One car can drive, say, from New York City to Los Angeles, CA in a straight line and cover a lot of ground in doing so. That one car cannot cover the US completely, from north to south, but a fleet of vehicles spread across several routes can.

What has been gleaned?

The MIT researchers found that 10 taxis typically cover one-third of Manhattan’s streets in a day and it takes about 30 taxis to cover half of Manhattan in a day. However, as taxis have convergent routes, over 1,000 taxis are required to cover 85% of Manhattan in a day.

Briefly put, the researchers found that “traditional deployments of sensors come with tradeoffs. Sensors on buildings, for example, can provide consistent daily data, but their reach is very limited. Putting sensors on vehicles is one solution. But which vehicles? Buses, which have fixed routes, cover limited ground. Members of the Senseable City Lab have fixed sensors to garbage trucks in Cambridge, Massachusetts, among other things, but even so, they did not collect as much data as taxis might.”

The MIT team’s study uses data from a variety of municipalities and private-sector research efforts to better understand taxi-coverage patterns. For deeper insights, a paper, “Quantifying the sensing power of vehicle fleets” is available. ~MD

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