Page 218 - Big Data Analytics for Connected Vehicles and Smart Cities

198 Big Data Analytics for Connected Vehicles and Smart Cities Practical Applications and Concepts for Transportation Data Analytics 199

safety, and efficiency benefits of VSLs is extremely important to transportation
practitioners. This fits within a wider need to understand the specific effects
of investments in smart city services and other transportation systems and in-
frastructure. While there is a great deal that can be done with data science and
analytics in transportation, this approach decided to focus on this relatively
narrow application as it provides an ideal opportunity to demonstrate the range
of capabilities of data analytics and provides direct input to a subject area that is
of importance to the state department of transportation in question.
The VSL approach involves the application of dynamic message sign tech-
nology to the control of traffic on interstate highways (freeways) around a ma-
jor urban area. Dynamic message signs placed at regular intervals along the free-
ways and connected via fiber-optic communications to a traffic management
center are used to display mandatory speed limits to drivers. The prevailing
speed limits are determined by measuring traffic conditions along the section of
freeway using roadside sensors.
As explained on the state DOT website:

VSL are speed limits that change based on road, traffic, and weather
conditions. Electronic signs slow down traffic ahead of congestion or bad
weather to smooth out flow, diminish stop-and-go conditions and reduce
crashes. This low-cost, cutting edge technology alerts drivers in real time
to speed changes due to conditions down the road. More consistent speeds
improve safety by helping to prevent rear-end and lane-changing collisions
due to sudden stops. Our ability to remotely change the speed limit on the
corridor is not intended to create speed traps. Rather, the changing speed
limits are designed to create safer travel by preventing accidents and stop-
and-go conditions.

The section of the regional road network that was the subject to this proof
of concept was equipped with 88 electronic speed limit signs at locations ap-
proximately a half mile to one and a half miles apart. The signs were located on
the outside shoulder and the median of the highway. The ability to change the
speed limits remotely is designed to create safer travel by managing stop-and-go
traffic conditions by creating smoother traffic. Speed limits are adjusted in 10-
mph increments from 65 miles per hour to a minimum 35 mph.
The VSL project began operation in September 2014, with the following
stated objectives.

• Reduce congestion and traffic delays by harmonizing traffic flow and
reducing traffic crashes;
• Reduce travel times;