Variable Speed Limit Signs

VSL UtahAt the recent National Rural ITS show held in Utah, a workshop was presented on the subject of variable speed limit signs. The speakers included Lynne Randolph from the Southwest Research Institute who talked about VMS use in Texas, Brian Christensen of Horrocks Engineers and Glenn Blackwelder of Utah DOT who discussed the local VMS installation on I-80 between Salt Lake and Park City, and Josh Crain of DKS who talked about the use of VMS in Oregon.

This technology remains one that makes good sense in theory, but whose complete affect on traffic is still not fully understood. This workshop filled in some of the blanks but there is more work to be done.

In short, a variable message sign system measures traffic speeds as conditions change and then displays the 85th percentile speed rounded down to the nearest 0 or 5 on regulatory speed limit signs upstream. The idea is to smooth traffic flow and reduce the speed variance that occurs as drivers begin to respond to changes in weather, traffic volumes and construction work.

The speakers shared some interesting lessons learned. Utah’s installation seemed to be the most successful. They have a total of 15 VSL signs through Parleys Canyon, a very steep climb from Salt Lake City east to Park City. There are 8 signs eastbound and 7 signs westbound. The other deployments discussed had far fewer signs or in Oregon’s case, they are single installations spread over the state.

Utah also posts VARIABLE SPEED LIMIT SYSTEM AHEAD signs at each end of the canyon. For these reasons they are far more visible and, I suspect, gets better results.

Utah did find that the white LED displays washed out behind a sign covered in the standard white reflective sheeting. To overcome this they added a black band around the speed display. You can see in the photo above that this change greatly improved the contrast so the signs are now easy to read in all light conditions.

The four speakers seemed to agree that drivers were more inclined to respect lower VSL speed limits when weather or construction activity justified the change. They did not respond as well when limits were lowered due to congestion downstream. Drivers need to know why they should slow before they respond.

Utah’s signs are enforceable. Texas’ signs are not. Oregon has installed some of each. They have developed a decision tree that weighs local conditions and the reasons for the installation to determine which type should be used in each situation.

It was a very informative workshop. I encourage you to download it when it becomes available.

What the Smartphone Supply Chain Can Do for Work Zone ITS

Today we welcome a new work zone ITS blogger: JP Story of Salander. He has written a guest post that I know you will find interesting!

Smartphones are the first technology to be bought by every human being on earth. This is pretty revolutionary in the technology sector, but also has some interesting implications in the Work Zone ITS industry. I’ll give you some background and show an example of how a former fishing village in China can increase work zone safety here in the United States.


It used to be that technology was sold to a subset of the population. You’d sell mainframe computers to Universities, Fortune500 companies and governments. You’d also sell Personal Computers to families and high schools. The addressable market of a product was always just a portion of the population. That’s not the case with smartphones. Roughly 2 billion smart phones have been sold to date.

Lets take a step back though and take a look at my first computer back in 1995. A blazing fast Packard Bell, with a screaming Intel Pentium Processor (the original!).

I’m sure you remember these beige boxes adorning the desks of the 90s.

Compare that Intel Pentium processor to today, 20 years later. The iPhone6 has 625 times the transistors (the basic unit of computing) as my old beige box. On the weekend the iPhone6 launched, Apple sold 25x the PC computing power that was on earth in 1995…in one weekend.

So today, everyone gets a pocket super computer.

Yes, everyone. Sub-Saharan Africa is one of the last places on earth to be blanketed in cellular airwaves. As you can see below, they are at about 70% population coverage. 3G is lagging behind but will catch up in the next 5 years. What’s really interesting about this graph is on the right side though. Roughly 37% of the population has a cell phone and yet only 33% of the population has electricity. More people value having a cell phone and being connected to the Internet than they do having electricity. While this poses some interesting problems when you have to negotiate with your neighbors and pay them to charge your phone…it really illustrates the trend that everyone on earth wants/needs a smart phone and access to the global communications network.

The main driver of this is the proliferation of cheap android handsets. Today you can buy a smartphone for $40. Below is an example I just googled, the Maxx MSD7 AX410. In India it costs 1500 rupees, or just under $40. That’s not with any 2 year contract where they subsidize the phone over time. This is $40 straight up, and includes a touch screen, battery, cellular module, Wi-Fi chip and most importantly, the ability to communicate to anyone on earth and learn anything on the Internet. For $40. The economies of scale that allow for this kind of downward pressure on costs is hard to fathom.


To really comprehend how amazing this is, you again have to go back in time. In the 80s, 90s and early 2000s, different tech sectors were more or less ruled by single companies. Microsoft was so famously dominant in the platform sector that they had an anti-trust lawsuit filed against them by the Department of Justice. Today, Apple and Google reap all the profits and are the big shots in platforms. Likewise in the chip world, Intel used to be the big dog. Now Qualcomm and ARM are where you’ll find all the growth. In the mobile space, you used to look to Nokia for a glimpse of the future. Now you look to Shenzhen China…our former fishing village.

Shenzhen Today


Shenzhen was the first of China’s “Special Economic Zones”, where they cut a swath of land and let free market capitalism run free. 30 billion dollars of foreign investment later, and you’ve got 10 million people living and working there, the vast majority in high tech manufacturing. So instead of having single companies enjoy the economies of scale, for the first time, you have an entire city of 10 million competing to drive costs down and deliver high tech products to the entire world. Nearly everything electronic you buy – smartphones, bluray players, TVs, laptops, game consoles – was either built there, or the components that make it up were built there.


So it used to be to create a new ITS product you’d spend 5 years figuring out how to create the chips and hardware and screen and so on. Now you go to Shenzhen and say, “I’ll take a number 4 chip and a number 7 screen with a type 2 battery”. Down the block is a manufacturer who will put it together in whatever configuration you want. The smartphone has enabled us to play Legos with technology. This has given birth to a bunch of new industries in the last 5 years, such as virtual reality, wearables, internet of things such as the Nest Thermostat, drones…the list goes on. What this will also catalyze is connected vehicles, infrastructure to infrastructure, and infrastructure to vehicle communication and collaboration. This is why we’ve seen such a surge in this space – it is all thanks to the smartphone supply chain, enabling our industry to innovate and move forward.
Historically, our industry has moved slowly, but there are glimpses of this new world on the horizon. Since everyone has a smartphone, Bluetooth and WI-FI detectors have surged in popularity as a way to combat the downsides of typical spot detection from loops and provide true flow data. Processing thousands of data points on a 12V solar system? It is possible thanks to low power draw yet incredibly powerful smart phone processors. Modern microwave sensors that incorporate cell modems and cameras from the smartphone supply chain. PCMS from some manufacturers, are full blown Linux servers, enabling a host of new features and awesome features (if only they were specified in).

How else will the smart phone supply chain affect our industry? How can we assemble these “Legos of Technology” in a way that can save lives? Stay tuned to the WorkZoneITS blog, where Joe is always looking to the future and sharing his insights. Also please checkout my new blog at, where we will be posting ideas and new ways of thinking of technologies role in work zones.
This post was inspired by the work of Bennedict Evans.