“What the heck is that?!”

That seems to be a common reaction of local motorists as they first encounter one of the flashing yellow arrow (FYA) traffic signals that have popped-up at San Antonio intersections over the past year or so.  What began as an experiment in late 2008 at a couple dozen intersections along Wurzbach Rd. and San Pedro Ave. has now spread to about 40 or so intersections across the city and will now become a standard, not just here in San Antonio, but nationally as mandated by the federal Manual on Uniform Traffic Control Devices (MUTCD).  As often happens in these cases, there has been some second-guessing amongst the general public as to the necessity of this newfangled signal, but understanding the research that went into it and why it’s beneficial generally allays those knee-jerk criticisms.

The purpose of the FYA signals is to indicate that left-turning vehicles must yield to oncoming traffic.  Previously, the solid green circular signal (”green ball”) was used, typically in a five-section cluster signal arrangement known colloquially to traffic engineers as the “dog house” display.  However, studies around the nation showed that this signal was often misconstrued by motorists to mean that they had the right-of-way.  This was especially true when it was used as part of so-called “Dallas phasing”, which extends the permissive left-turn time at an intersection by de-coupling that left turn movement from the adjacent through movement.  In other words, the left turn lane could have a green ball while the adjacent through-traffic lanes could have a red light.  A few Dallas-phased signals were installed in San Antonio in the Medical Center area, and I can tell you from experience that many drivers are quite confused by them.  However, Dallas phasing provides a big benefit in the form of more efficient intersection flow because left turns can be made at any time during the phase (when traffic is clear, of course) instead of only when adjacent through traffic also has a green, thus allowing more vehicles to get through during each cycle and reducing delays for left-turning drivers.  Dallas phasing also solves the problem of the “yellow trap” that occurs when a circular yellow light is displayed to traffic waiting to make a permissive left turn while, at the same time, opposing through traffic still has a green light.  This usually causes those left-turning motorists to presume oncoming traffic is about to stop and that it is safe to complete their left turn when in fact it is not.

So, to capture the benefits of Dallas phasing without the inherent safety issue involved with using a green ball signal for permissive lefts, engineers across the country tried a variety of other displays and several studies were done.  The one display that had the greatest inherent understanding was the FYA.  More importantly, the FYA had the lowest “fail-critical” rate, which means that drivers were less likely to do the “wrong” thing if they didn’t understand what the signal meant.  In other words, drivers that see a FYA and don’t understand it are more likely to yield whereas drivers who see a green ball are more likely to proceed.  The reason for this is easy to explain: people inherently understand a flashing yellow light to mean “caution” while we instinctively interpret a green light to mean “go”.  It’s also worth noting that the FYA indication has been used successfully in parts of Europe for many years.

As a result of these outcomes, the Federal Highway Administration has designated the FYA as the standard signal display for protected/permissive left turn signals in the latest release of the MUTCD, which was promulgated last December.  Additionally, no signal displays with a solid green ball signal can be placed to the left of the lane line between the left turn lane and the adjacent through traffic lane.  In other words, left turn lanes cannot have a dedicated signal that has a green ball display.  Of course, it will take quite some time to retrofit existing signals to meet the new standards, and the MUTCD has set no target date for full replacement.  However, all new signals and refurbishments of existing signals will have to be compliant going forward.

Additional reading:

• Interim Approval for Optional Use of Flashing Yellow Arrow for Permissive Left Turns
• Evaluation of Traffic Signal Displays for Protected/Permitted Left-Turn Control (NCHRP 3-54 Research Project)
• 2009 Manual on Uniform Traffic Control Devices
• Google search for “flashing yellow arrow”

The oft-maligned 1604/Braun intersection

Well, once again, it’s been a while since I’ve posted anything here.  I’ve been working on what I think will be an exciting new addition to my website (stay tuned for more on that soon.)  However, as I was watching the Sunday morning political talk shows, my wife mentioned something that motivated me to write this post, which is one that I’ve been meaning to do for a while.  While Facebooking (can that really be a verb?), she came across a new Facebook group with the same title as this post.  After rolling my eyes (as I often do in these situations), I realized (also as I often do in these situations) that the creator of that group– and those who subscribe to the explicit as well as implicit sentiment of it– probably just doesn’t have the back-story to understand why things are the way they are and that my initial reaction made me just as guilty of jumping to conclusions as that person was.  Whoever created the group is obviously frustrated– they even say they’re “pissed off” at the “stupid” traffic lights, and I sympathize with their frustration.  But, as is often the case, there’s more to the story than meets the eye, and maybe if folks understood how things got to be as they are, they might be more forgiving.  This posting is an attempt at that.

First off, I can tell you that the local TxDOT folks don’t like the way things are out there any more than anyone else does.  If they had their way, there would be a nice, high-speed expressway all the way from Braun to US 90.  And the traffic signals that are there weren’t put there capriciously– as with any traffic signal, there are a number of technical “warrants” that must be met before a signal can be installed.  But more on both of those topics in a bit.

History
Perhaps a look back at the history of Loop 1604 West might be beneficial and help put things into context.  Fifteen years ago, the Loop 1604 expressway that runs across the Northside ended at Babcock.  Loop 1604 south of that big curve near Babcock was just a two-lane rural road.  (In fact, you can still see where the lane lines for the transition from expressway to two-lane road have been scrubbed from the pavement just south of that curve.)  Other than a lonely overpass for 1604 over SH 16 with a couple of jughandle ramps connecting the two roadways, it was just a run-of-the-mill farm road with some traffic signals at Hausman, Braun, Culebra, and Potranco.  (I can even remember back in the ’80s when the intersection of 1604 and Culebra was a four-way stop.)

With traffic dramatically increasing on the northwest side, work was completed in 1996 to extend the expressway from Babcock down to Braun.  South of Braun, Loop 1604 remained a two-lane road until 1999 when work to upgrade it to a divided highway as far as Culebra was completed.  At the time, that was a considered by everyone to be a significant improvement, but TxDOT intended for it to just be an interim step until funds could be obtained to extend the expressway from Braun all the way south to US 90.  One element of that overall vision– an overpass at Culebra– was funded separately and was completed in 2004.  

South of Culebra, work to upgrade 1604 to a divided highway was completed– after several delays due to utility issues– in 2007.  Again, this work was done with the ultimate expressway plan still in mind.  In fact, the section south of SH 151 was specifically designed to allow for a quick upgrade to a expressway.  The existing northbound lanes will be the future northbound access road.  The existing southbound lanes will be the future northbound mainlanes, with overpasses of course added at the major intersections.  That leaves just the overpasses, entrance and exit ramps, and southbound mainlanes and access road to be constructed. 

Why no freeway?
As I mentioned above, TxDOT’s plan for the area has always been to build a full-fledged expressway all the way down to US 90.  TxDOT’s project plans statewide have always been financially-constrained, so they’ve always had to make trade-offs and take a phased approach at completing projects (just like I have to do on making upgrades and improvements to my house.)  Loop 1604 West is a case in point.  By the mid ’90s, it was apparent to TxDOT’s planners that sufficient funding for an expressway was at least a decade away, if not longer, but the congestion in the Loop 1604 West corridor had increased so rapidly that it needed an urgent fix.  Therefore, to provide some immediate relief to motorists,  TxDOT opted for the cheaper surface-level divided highway to allow it to be funded and built sooner.  And indeed, the road that’s there today is a considerable improvement over what was there before, and given the severe funding shortages that TxDOT is having these days, it was actually good foresight on their part to get something done when they did instead of waiting for funding that probably still would not have come to this day.

As I mentioned above, the overpass at Culebra was the first element of the planned expressway to be completed.  Due to the high volume of cross-traffic on Culebra, it was chosen for an overpass before Braun or other intersections.  Unfortunately, funding has not been available to complete any more of the ultimate expressway plan since.

What’s next?
In late 2003, the Texas Transportation Commission, at the behest of the governor and as a result of diminishing gas-tax purchasing power (a problem that continues to this day), ordered that all planned expressway projects statewide be considered for tolling in order to expedite funding for their construction.  Therefore, the Loop 1604 West expressway project was evaluated and determined to fit the established criteria for a toll project.  In 2007, the Alamo Regional Mobility Authority (ARMA) opted to exercise their right under state law to assume the project from TxDOT in order to maintain local control of it.  As a result of the lawsuits stemming from the US 281 tollway brouhaha, ARMA decided to perform a new environmental and needs study for all of Loop 1604, including Loop 1604 West.  That study is ongoing and no major improvements can be made to 1604 until that study is done, which currently is expected to be in 2012 with construction on any improvements starting no sooner than 2015.

In the meantime, at the request of ARMA, Bexar County recently funded a study about implementing a “super-street” on 1604 from Braun to SH 151, like the one that will be built on US 281 this summer.  The results of that study are set to be announced within the next few weeks.  If approved, the 1604 super-street, like the one on 281, could be built fairly quickly and is intended to be a short-term band-aid until a permanent, long-term solution can be built.

Signals, warrants, and synchronization
Most of the signals that are on Loop 1604 today have been added over the past decade or so as a result of traffic demands.  As I mentioned earlier, traffic signals cannot be added to a roadway unless they meet a number of technical requirements (known as “warrants”), including through-traffic volumes, turning movements, intersection geometry, and crash history.  Engineers are reluctant to install signals on a road like 1604 unless absolutely necessary due to the interruption to traffic that they cause.  The signals on 1604 may be disruptive and annoying, but they do serve a legitimate purpose and were carefully considered before being installed.

Some folks will ask why can’t the signals be synchronized.  The problem is that the signalized intersections on 1604 are located at such distances that synchronization would not function as desired.  For synchronization to work properly, intersections typically need to be a half-mile apart or less to allow for the tight “platoons” of vehicles to be properly maintained through the corridor.  Vehicles must be within the scheduled timeframe (known as a “green band” or “green wave”) for a platoon in order to get a green at each successive signal.  The longer the distance between signals, the more likely the platoons are to disperse, thus negating the synchronization.

Another issue plaguing Loop 1604– and 281– is that during peak periods, there is simply too much traffic.  When traffic volumes exceed the roadway capacity, signal synchronization inherently breaks-down because traffic queues build-up at each intersection and those queues exhaust the green time that was intended for the platoon of vehicles coming behind them.  That platoon then gets caught entirely or partially by the subsequent red light, thus perpetuating the cycle until traffic volumes drop back below the capacity of the roadway.  In short, signal synchronization is not always the “magic bullet” that most people believe it to be.

It’s worth noting the traffic signals along Loop 1604 are managed by the City of San Antonio, so any complaints about their operation should be reported to COSA Public Works.

A problem of perception
Frankly, I think many complaints simply stem from misperceptions on the part of motorists and the perhaps unrealistic expectations those misperceptions bring.  First of all, the majority of folks living in the 1604 West area nowadays are new arrivals, having moved to the area in the past decade, and therefore don’t know what things were like before.  They’re making their judgements based on what they see today and not realizing that things once upon a time were much worse.  Are things perfect today?  Of course not, and there will always be room for improvement.  But the situation today could have been far worse than it is.

The second perception problem– which is the same one that plagues 281 north of 1604– is that many people consider 1604 West to be a “highway”, and so they believe it should function like Loop 410, I-10, or Loop 1604 north of Braun.  But those roads are all expressways, and the fact is that 1604 south of Braun is not a “highway” in that sense, but instead is just a regular surface-level divided highway.  As such, it is functionally the same type of road as SH 16 (Bandera Road), and I rarely– if ever– hear people complain that the signals along Bandera are incongruous.  A divided highway is not automatically an expressway, and just because other parts of 1604 are an expressway doesn’t mean that all of it is– that’s why there are the “END EXPRESSWAY” signs on southbound 1604 approaching Braun.  Just look at the Google Map of the area– notice that the thick gold roadway (which is how Google Maps denotes an expressway) ends at Braun and the yellow roadway that is used for 1604 south of there is the same as the one used for Bandera, SW Military, Austin Hwy., and other non-expressway state highways in the area.

So, to borrow Paul Harvey’s famous line, now you know the rest of the story.  I don’t expect an “I love the Loop 1604 traffic lights” Facebook page to be born as a result, but I do hope this has helped explain how the situation on Loop 1604 has evolved and why the folks responsible for the signals out there don’t really deserve to be the targets of road angst.

Links of interest:

• Texas Highway Man: Loop 1604
• Texas Highway Man: Loop 1604 Tollway Project
• OnTheMoveBlog: Loop 1604 Super Street to be studied
• WOAI-TV: ‘Superstreet’ planned for Loop 1604 on Northwest Side
• More for 1604 (enviro study)
• Manual on Uniform Traffic Control Devices: Traffic Control Signal Needs Studies
• Wikipedia: Green wave

While walking to lunch with my colleagues, we stopped for a “don’t walk” signal at one of the scramble intersections.  One of them noticed that the signal for vehiclular traffic headed our direction was green but that we had a “don’t walk” signal and instinctively realized that something was amiss.  Ah, she must not have read my blog!  (Doesn’t everybody?)  After I explained what was afoot (pun completely intended), she commented that she was really happy with the new configuration and couldn’t wait to cross diagonally– it was like being able to finally do something that had long been verboten.

While out and about, I noticed many other people taking advantage of the diagonal crossing ability.  I did see a couple of instances, though, where people were crossing against the light and obstructing turning vehicles, thus thwarting the intent of the project.  Over time, I’m sure people will understand and adjust to the changes.

For years, I have hoped that the city would install these.  They eliminate the problem of having to wait for pedestrians to clear when making turns.  When pedestrian traffic is heavy, that severely inhibits the number of vehicles that can make a turn while the light is green.  Add to that the fact that most people don’t know that it’s perfectly legal to make a left on red when both streets are one way and sometimes it can take several signal cycles to make a turn at some intersections.

Pedestrian scrambles eliminate this problem because pedestrians only have a ”walk” sign during their exclusive phase or if their crossing does not interfere with turning traffic.  The rest of the time they have a “don’t walk” sign, even if the signal for parallel vehicular traffic is green.  Because it removes that conflict, it also improves safety for pedestrians.  In fact, one study showed a 50% reduction in pedestrian/motor vehicle accidents.

Unfortunately, during my last trip downtown, the three intersections that I think especially need this system didn’t have it yet– the three intersections around Convention Plaza (the triangle around the big orange “Torch of Friendship” statue.)  That right turn from Commerce to Alamo and the right turn from Lasoya to Commerce can be a real pain due to pedestrian volumes at those crossings.  Hopefully those intersections will get this badly needed improvement soon.

In the meantime, here are the intersections that were active last week:

• Commerce/Flores
• Flores/Nueva
• Houston/Navarro
• Houston/St. Mary’s
• Travis/St. Mary’s
• Travis/Navarro
• St. Mary’s/College

The following had the equipment installed but were not active yet:

• Flores/Dolorosa
• St. Mary’s/Market
• Market/Navarro
• Market/Presa
• Commerce/Presa
• Commerce/Navarro
• Commerce/St. Mary’s

UPDATE: Found two more locations on 2/8/10 that were probably there earlier but I just missed them:

• Navarro/Crocket
• Navarro/College

UPDATE: Pedestrian scramble update

Links:

• Wikipedia
• Livablestreets.com/StreetsWiki
• Walkinginfo.org/PEDSAFE

Scramble crossing at Commerce and Flores