Calling all cars: cell phone networks and the future of trafficPresentation by Scott CoreyArticle written by Haomiao Huang

The Future of Cars Self-driving cars? Boosting the brainpower of the

environment cars drive in Traffic monitoring has been

revolutionized

An intelligent highway Reducing the effect of traffic jams and

accidents Traffic control schemes to react to real

time data Aid in planning for the future

Sensors Monitor traffic Parking availability Air pollution Have traditionally been static sensors

Inductive Loop Detectors Traffic Cameras RFID tags

Problems Expensive to deploy, operate, repair Placed only at key locations

Mobile sensors are a necessity

Mobile Phones Equipped with GPS and Internet access Smartphones enable more widespread

source of data

Worldwide, there are more cell phones in use than toothbrushes

Mobile Millennium One of the first large-scale phone-based

traffic monitoring projects in the US Run by Nokia, NAVTEQ, and UC Berkeley

Gathering data, but privately User privacy is key for user acceptance Two main needs:

Preventing the path of a vehicle to be reconstructed

Separating the identification of the phone from the data

Anonymity Data from phones is tagged with user

information The data packet is encrypted at

transmission Proxy server cannot decrypt packet, but

can strip identifying information Sent to traffic servers after information

stripped

Reconstructing paths Uses virtual trip lines instead of

constant reporting VTL spacing varies based on speed to

maximize number of cars Randomizing measurements

Making sense of it all UC Berkeley tasked to fuse all the data together GPS from phones GPS data from dedicated vehicles Static sensors

Given all of the measurements being gathered and a stretch of road of interest, what is the best estimate of the number of cars on that road, and how fast they're going?

Combining data with maps GPS tracks are useless alone – need to

combine with maps to know what road network you are monitoring

Measurements have to use machine-learning methods to correct for people walking with phones, parked cars

The flow of traffic Tracking thousands of cars individually

is difficult and expensive Traffic researchers treat movement of

cars as liquid flowing through tubes

Fluid Dynamics

Requires initial conditions and rate of cars entering/leaving roadway

Fluid dynamics model works well with fixed sensors

Cameras can determine initial conditions

Sensors attached to on and off ramps

Disruptions Drivers are not perfect

Accidents Unnecessary slow-downs

Adding GPS dramatically increases the versatility of the fluid model

GPS incorporated as internal conditions for the flow to satisfy

Mobile Century Proof of concept test 100 cars with mobile phones mixed into

traffic Ran for 10 hours with 150 student drivers Despite accounting for 2-5% of cars on

the highway, speed and density of cars measured at a high resolution

Accident was detected and reported in less than a minute

Till all are one Concepts and technology are now

widespread Mobile sensors used to identify potholes

in roads Connections to vehicle sensors Mobile sensing is the future