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E-ZPass Tags Could Help Create Smart Cities

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【Summary】Researchers at MIT have developed a method that involves using E-ZPass tags for vehicle to infrastructure communication. This could help pave the way for smart cities.

Mia Bevacqua    Aug 24, 2017 2:35 PM PT
E-ZPass Tags Could Help Create Smart Cities

We've got smart phones, smart watches and even smart houses – so why not smart cities? Such infrastructure would improve urban life in many ways. Unfortunately, current technology is too expensive and/or unreliable. But, a couple of researchers at MIT are working on an answer.

A new use for E-ZPass tags

Dina Katabi and Omid Abari have developed a small solar-powered unit called a Caroake. The device is designed to measure the speed and position of up to 20 vehicles equipped with E-ZPass transponders. If you're not familiar, these are the tags used on the East Coast to allow drivers' passage onto toll routes.

E-Pass transponders emit a radio-frequency signal that can be requested. So far, only highway readers have been chatting with E-ZPass tags, asking drivers for their credit cards. What the researchers figured out is that anyone can strike up a conversation with an E-ZPass to gain vehicle information. 

Caroakes could be positioned at various locations throughout the city to track vehicles. This could aid in directing traffic, parking control and much more. 

How it works

Instead of querying a single car, Caroakes activate all E-ZPass tags within a 30-meter range. To avoid signal collision when a group of cars respond at once, the MIT researchers have came up with a clever idea. They cash in on the fact that all E-ZPass tags broadcast to the one side or another of their 915-megahertz frequency. This discrepancy is referred to as the tag's carrier frequency, and is used to differentiate one tag from another.


To localize each tag, a pair of antennas is used to calculate the signal's angle of arrival. Moving vehicles require two or more antenna pairs used together. After the information is gathered, the Caroake units transfer their data to smart city servers via Wi-Fi or cellular LTE

Just how well do the Caroake work? In tests conducted by MIT, the units could determine speed within 8 percent and location within 4 degrees.  

Implementing the System

Not surprisingly, the biggest concern with Caroakes is driver privacy. Many people don't like to be tracked – period. 

To counter this problem, the MIT duo will calculate only the carrier frequency of the E-Zpass tags, not the identifying data bits. Even so, getting drivers to accept the fact they're continuously being tracked could be tough. 

And if they don't want to be monitored, drivers will simply remove the tags. This presents a major problem, since every vehicle in the city needs to be equipped with a transponder for the system to work.

Current E-ZPass toll booth systems are on the rise. In certain states, their usage is at 80 to 90 percent. This provides a ray of hope that we may have a smart city one day – with a little help from the Caroakes, of course. 

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