Travel Time signs

[GaryV]

I've been amazed at how Google Maps manages to track slowdowns.  They must process billions of incoming points of data and then spit it back out to phone apps.

The GPS in your phone. Seriously. They track phone locations.

I know - but then they have to crunch all the numbers of all the phones on the road to figure out how fast traffic is going on all the miles of highway and city roads.

[vtk]

I've been amazed at how Google Maps manages to track slowdowns.  They must process billions of incoming points of data and then spit it back out to phone apps.

Google has become exceptionally good at doing exactly that.

[1995hoo]

The signs we saw yesterday here in Phoenix listed only the travel time and not the distance. Not too helpful for anyone who doesn't know the area!

[OCGuy81]

The signs we saw yesterday here in Phoenix listed only the travel time and not the distance. Not too helpful for anyone who doesn't know the area!

Sounds just like southern California.  The way to spot a visitor is they'll ask how far something is in terms of mileage.

Locals always measure distance in time.  It's 45 minutes away (which could be only 5-6 miles).

[1995hoo]

The signs we saw yesterday here in Phoenix listed only the travel time and not the distance. Not too helpful for anyone who doesn't know the area!

Sounds just like southern California.  The way to spot a visitor is they'll ask how far something is in terms of mileage.

Locals always measure distance in time.  It's 45 minutes away (which could be only 5-6 miles).

Which is fine if you know how long it usually takes. At home the sign might say "I-495/9 miles/35 minutes." In that case, the average driver can tell it's at a crawl even if he doesn't know the road. But a sign like the one on I-17 last night that simply said "Northern 8 min" didn't tell me anything. Had I been the driver, I would have wound up watching to see whether other people were bailing out at the next few exits. (Didn't matter much because my brother-in-law was driving and he lives here.)

[davewiecking]

Yes, I read that as Time Travel signs.

My understanding is that a company called Inrix is responsible for pulling down cellphone tracking data from wireless phone companies, tweaking it, and reselling it to various highway departments for this purpose. They have a nice App that provides this information. As noted, this isn't the only way this data gets to the signs.

[JoePCool14]

Indiana has these all over Indianapolis and Northwest Indiana. In fact, I believe I had a post here a few years ago where I erroneously titled it "Time Travel Signs" with people joking about that before I realized what I had written and changed it. The Indy ones are relatively useful when it comes to rush hour and finding out how long it may take to get to certain points but for non-rush hour periods they are about as helpful as the ones in Ohio. One thing the Indy area also has along I-65 and I-70 is posted travel times through the city and around the beltway to state which route is quicker (it's almost always the thru route, except for rush hour.)

I was recently in Los Angeles and I kept on thinking to myself, "God do you guys need these." I know they had VMSs around annoucing travel times in some spots but if only you had lots and lots of these signs all over your freeways, they could be helpful.

I quite like the way they are installed around Indianapolis. I'm sure they also require less electricity, as only the number of minutes is displayed.

[Brandon]

IDOT uses the acoustic detectors and the loop detectors around Chicagoland.  ISTHA uses I-Pass transponders.  Both post the travel times on the VMSs throughout the area.

[Truvelo]

I believe here they use cameras sampling a certain amount of vehicles they read part of the license plate and cameras x amount of miles further along can then calculate the speed.

One thing is for sure. The time shown will never be less than what can be achieved by staying within the speed limit.

[DrSmith]

As far as the CT time measurements go, I have noticed they only use certain amounts of time.  From what I have seen its 4, 6, 8, 10, 13, 16, 20, 25, 30, 35, 40, 46, 52.... in minutes.  So on I-91 south in Windsor, the best it ever says is 7 miles 8 minutes even when there traffic is flowing easily, although I have seen 30 minutes listed. But the times can be faster, with the one on I-91 south after Exit 28 reading To Route 9, 7 miles, 6 minutes.

However if anything in the morning the updates can lag behind how traffic is building. Recently I have noticed that it is best to assume the next increment up from what is listed, and this is driving in the left lane and I don't have to wait in the right lane to exit to 84 west.

You can occasionally catch the updates because the screen flashes for a moment.

[cpzilliacus]

Many state transportation agencies ("free" and toll roads) and some local governments purchase data from Inrix (or competitor companies, such as TomTom and Here) to compute travel times for use on dynamic message sign units.

Where does Inrix get these data?  From its fleet of probe vehicles, including drivers that are using the Inrix app on their smartphone or similar device.

[Kacie Jane]

I believe here they use cameras sampling a certain amount of vehicles they read part of the license plate and cameras x amount of miles further along can then calculate the speed.

One thing is for sure. The time shown will never be less than what can be achieved by staying within the speed limit.

That last point is true in Washington State, and I'm sure various other places, but not universal. I believe in other similar threads, it was mentioned that Florida doesn't follow this rule?

[UCFKnights]

I believe here they use cameras sampling a certain amount of vehicles they read part of the license plate and cameras x amount of miles further along can then calculate the speed.

One thing is for sure. The time shown will never be less than what can be achieved by staying within the speed limit.

That last point is true in Washington State, and I'm sure various other places, but not universal. I believe in other similar threads, it was mentioned that Florida doesn't follow this rule?

Yes, I've definitely seen in Orlando roads with 50-55mph speed limits that have travel times with numerous less minutes then the number of miles you need to travel.

[Brandon]

Many state transportation agencies ("free" and toll roads) and some local governments purchase data from Inrix (or competitor companies, such as TomTom and Here) to compute travel times for use on dynamic message sign units.

Where does Inrix get these data?  From its fleet of probe vehicles, including drivers that are using the Inrix app on their smartphone or similar device.

Inrix does not supply IDOT or ISTHA with that data.  IDOT uses loop detectors and acoustic detectors in the six county Chicagoland area (IDOT District 1), and it is well known and well publicized that ISTHA uses I-Pass transponders.

http://www.travelmidwest.com/lmiga/faq.jsp

4. Where does the information come from?

The system receives traffic data from all major traffic management systems in the area, including the Illinois, Indiana, Wisconsin, Michigan, Minnesota, and Iowa Departments of Transportation, the Illinois Tollway, the Chicago Skyway, the Indiana Toll Road, and the City of Chicago and Lake County Illinois Divisions of Transportation. These systems use a wide range of traffic detection technologies to monitor speed and concentration of vehicles. Based on the collected data, traffic congestion levels and travel times are computed. These systems also provide messages currently displayed on dynamic message signs located along the roadways.

Information about incidents and construction-related road closures is received electronically from several site contributors. Additional information is entered manually by Travel Midwest operators from a series of reports, and the operators also check and correct the automated accident entries. This blend of automatic data and manual entry help to keep the information available to drivers as current and accurate as possible.

5. How does automatic traffic data get to the system?

There are currently many types of vehicle sensors available, including inductive loop, microwave radar, infrared, ultrasonic, acoustic, and video image processing. There are embedded in-roadway sensors and above-roadway sensors. The Gateway System has a blend of both types. In general, these sensors detect the presence and passage of vehicles.

The collected data is transmitted from the field via a variety of communication links to a central control system, where it is further processed and distributed.

7. Why does the travel time and congestion information disappear when there are major construction projects, when we need the information the most?

Unfortunately, most major construction projects involve removal of the existing roadbed and other activities that interrupt the operations of the traffic sensors and/or their communication to the central control system. Once the construction activities are over, operation of the affected traffic sensors are restored. Until then, there is no way to get the data.

Occasionally, a project will allow for the installation of temporary sensors to fill the gap during construction, but this is not always feasible. Every effort is made to bring the sensor systems back into operation as soon as possible.

So much for the Inrix fleet.

30. Why are the Illinois Tollway congestion levels and travel times sometimes less accurate?

The Gateway system gets data from a variety of sources - Illinois DOT, Illinois Tollway, Indiana DOT, etc. These agencies use a variety of mechanisms to provide their raw data - pavement loop detectors, transponder toll tag timestamps, etc. In the case of toll tag transponders, the data is by nature coarser and potentially less timely than direct roadside-based systems. In particular, these data can suffer from latency issues because of delays in receiving the same. For example, if motorists are delayed by heavy congestion, the system is initially unaware of this problem until the motorist passes through the congestion and reaches a toll plaza (or exit) where the toll tag is read. That situation inevitably results in extra delay before the end point timestamp is read. Additionally, the system is unable to determine the precise location of congestion since the data only indicate a delay between two points sometimes spaced far apart (for example 2 toll plazas). This results in long map segments with the same color congestion coding.

The Illinois Tollway is expanding the sources of data used to provide travel times to the Gateway which will allow more granular congestion data to be presented in the future. At a minimum, congestion data will be provided between entrances and exits to the system.

Finally,

What is the Great Lakes Regional Transportation Operations Coalition (GLRTOC)?

The Great Lakes Regional Transportation Operations Coalition (GLRTOC) is a partnership of Great Lakes agencies that collaborates on initiatives that improve cross-regional transportation operations in support of regional economic competitiveness and improved quality of life. The GLRTOC members are agencies that have transportation operations on the major routes connecting Minneapolis to Toronto and include the Illinois Department of Transportation, the Illinois State Toll Highway Authority, the Indiana Department of Transportation, the Indiana Toll Road Concession Company, the Iowa Department of Transportation, the Michigan Department of Transportation, the Ministry of Transportation Ontario, the Minnesota Department of Transportation, the Ohio Department of Transportation, the Skyway Concession Company, and the Wisconsin Department of Transportation.

[mrsman]

Indiana has these all over Indianapolis and Northwest Indiana. In fact, I believe I had a post here a few years ago where I erroneously titled it "Time Travel Signs" with people joking about that before I realized what I had written and changed it. The Indy ones are relatively useful when it comes to rush hour and finding out how long it may take to get to certain points but for non-rush hour periods they are about as helpful as the ones in Ohio. One thing the Indy area also has along I-65 and I-70 is posted travel times through the city and around the beltway to state which route is quicker (it's almost always the thru route, except for rush hour.)

I was recently in Los Angeles and I kept on thinking to myself, "God do you guys need these." I know they had VMSs around annoucing travel times in some spots but if only you had lots and lots of these signs all over your freeways, they could be helpful.

Los Angeles was among the first areas to use the VMS signs.  The famous "freeway condition" sign that were prominently featured in the movie "LA Story".  Originally, they would list information like construction and accidents - the same type of infor you can get from the radio.  The signs only seem to be on when there is a problem.

Eventually, they will be used for constant information like miles and minutes.

[MASTERNC]

PennDOT is inconsistent with travel time signs.  Half the time they aren't running on I-76 (at least between US 202 and I-476), even when there are major backups down the road.  They also don't report every incident that slows down traffic.