The city is coming to the end of its five-year contract with Redflex for the management of its red light camera program. The contract expires April 1. We now have a great opportunity to correct some serious problems with our current system.
Before I get deeper into this, please let me make something clear. I am not necessarily advocating for the removal of the cameras. While the removal of the cameras is one option the city has to correct the problems I will address, that decision ultimately rests with the city’s elected officials.
What I am advocating is the extension of the left-turn arrow duration at our intersections from 3.5 to 5 seconds, to match the time of the straight-through yellow at the same intersections.
While the request is simple, the reasons behind it require a less-than-simple and more scientific explanation. That will be done below. The safety of our intersections has to be the No. 1 factor in any decision our city makes.
The city is standing behind the camera enforcement because its statistics show a decrease in collisions caused by red-light running at the intersections that are being monitored.
I have done an extensive analysis of the collision data using the data from the California Highway Patrol’s Statewide Integrated Traffic Reporting System (SWITRS) database and find it inconclusive in giving the cameras the credit for the reductions.
The number of accidents per intersection before and after the cameras is too low to give a meaningful percentage change. The report does not take into account that there are other factors relating to red light running like impaired and distracted driving that cameras have no effect on. Also, rear-end collisions have increased at the camera intersections, which more than offsets any reduction in red-light running collisions.
Even if it were conclusive that the cameras are reducing accidents, we cannot ignore the large number of our citizens and visitors being unfairly cited with a $490 ticket for a red-light violation they were essentially trapped in. The people I am referring to are the left-turning drivers facing a 3.5-second yellow arrow.
In 2010, 96 percent of all violations were for left turns and 74 percent of the total were within 1 second of the light turning red. There are charts available from Redflex on HighwayRobbery.net that clearly show this for the third quarter of 2013. Some of the intersections show zero violations in the straight through lanes.
Here is one chart for one left turn lane (Lane No. 2) from the intersection of northbound Bouquet Canyon Road and Newhall Ranch Road for the third quarter 2013. While this is just one lane at one intersection, you will see the same pattern repeated in most of the intersection charts.
The reason this pattern of violations is happening is not a surprise. It is due to a “dilemma zone” that exists in our left-turn lanes because the yellow arrow duration is too short for the actual speed of the vehicles approaching the intersection in long left-turn pockets.
Drivers caught in this dilemma zone when the green arrow changes to yellow do not have enough distance to stop using a reasonable rate of deceleration before entering the intersection and do not have enough time to enter the intersection before the light turns red. It is not their fault they were forced to enter on red due to the dilemma zone.
Not every driver turning left at our camera intersections will have the yellow light illuminate when they are in the dilemma zone. But many have been caught in the dilemma zone and have gotten tagged with a $490 citation for crossing the limit line only a fraction of a second after the light turned red. These are the folks who are shown in the chart above.
Our city’s left-lane dilemma zone existed before the cameras were installed. In fact, a dilemma zone exists at all long left-turn lanes in the city where the yellow time is set at 3.5 seconds rather than the same time as the through-yellow light. The cameras have actually performed a public service to show proof that the dilemma zone exists.
Unfortunately, the cameras have also caused some drivers to slam on their brakes in order to avoid that $490 ticket. As a result, rear-end collisions are up 16 percent at the red-light camera intersections since the cameras were installed.
The cameras have been in place for at least eight years, yet the city continues to issue more than 8,600 tickets per year. Why have drivers not adjusted their behavior not to run the red light by a fraction of a second in left-turn lanes? The answer is they can’t. To change is impossible, because it defies the laws of physics. This will be explored in some detail below.
Redflex is well aware of the dilemma zone, and it has used this knowledge to fleece these otherwise safe drivers. Redflex and our city are generating a huge amount of revenue from these citations. Our city has a moral imperative to stop citing these drivers and saddling them with a $490 fine.
Next I will get into the science of the dilemma zone at our intersections. Much of this I learned from Jay Beeber, executive director of Safer Streets L.A. He is a research fellow with the Reason Foundation and has recently served on a subcommittee of the California Traffic Control Devices Committee, studying the proper setting of yellow signal times in California. He is a committed advocate for safer streets and reasonable traffic enforcement in the state.
Santa Clarita’s Left Turn Pocket Dilemma Zone Explained
The paragraphs above give a good overview of how the dilemma zone created by the short left-turn arrow is a real problem. This section is intended for the reader who wants a more complete explanation of exactly why the zone exists in our city.
To begin, we need to look at how yellow light duration is determined for straight through lanes. Our city, as most, uses the Manual on Uniform Traffic Control Devices (MUTCD) to determine yellow light durations. There is a table in the manual that proscribes the minimum yellow interval based on the speed of the traffic approaching the intersection (not necessarily the speed limit). It is Table 4D-102. Here it is:
I will use the example of a driver approaching our intersections at 50 mph for all comparisons done in this section.
You can see in the chart that the minimum time for the yellow at that speed is 4.7 seconds. I have confirmed that our city used this chart, then added 0.3 seconds, to result in a 5-second yellow interval throughout the city on straight-through lanes. This has worked well for our straight-through lanes. The yellows are the right duration. This is a key reason we see so few red light violations on the straight-through lanes compared to the left-turn lanes.
The values in the table are calculated using the Institute of Transportation Engineers (ITE) Kinematic Formula. While the formula and the table work well for straight through lanes, it cannot be used for left-turn lanes. Drivers traveling straight through the intersection and maintaining their speed throughout their approach need the minimum amount of yellow time listed in the table based on their approach speed. Drivers in turning lanes that are approaching at the same speed need at least the same amount of time.
The physics which control whether the driver is able to stop does not change simply because the driver will later slow down to make his turn once he is closer to the intersection. The physics that determine the yellow time this driver needs is based on the driver’s initial approach speed, not his turning speed. And in a long left-turn pocket, his approach speed might well be the same as the speeds in the through lanes.
However, the left-turn driver, as opposed to his straight-through counterpart, must also slow down to about 20 mph in order to safely negotiate the left turn. This slows him down a bit, and therefore it takes him a little longer than his straight-through counterpart to get to the intersection. So a driver approaching in the left-turn lane needs at least as much time as his straight-through counterpart, plus a little more time to account for the fact that he also has to slow down.
Unfortunately, the MUTCD does not address this situation in detail and leaves it up to the traffic engineer to use his judgment as to how long the yellow time needs to be in turning lanes.
The MUTCD states the minimum must be 3 seconds. It leaves it to each city to determine what is right for its own left turn lanes. Our city has chosen to add 0.5 seconds for “extra safety.” There has been no scientific process used in that determination. Three and a half seconds is just plain wrong for the long left-turn pockets that exist in our city.
As stated earlier, most of our left-turn drivers will go through the intersection without encountering the dilemma zone. However, it is not unusual to have a driver safely approaching at 50 mph in the left turn lane, when they encounter the yellow arrow. If this were a straight-through lane, the table tells us this driver needs 4.7 seconds to clear the critical stopping distance of 343 feet. If the driver is farther away from the intersection, they can safely stop, but if they are closer than the critical stopping distance of 343 feet, they must keep going, and it will take at least 4.7 seconds for them to get to the limit line.
But the signal is set for only 3.5 seconds. The further problem for this left-turning driver is that he must keep going but also must slow down to 20 mph to negotiate the turn. He will actually need more time than the 4.7 seconds, and clearly more than 3.5.
The 3.5-second interval we currently give would work for a straight-through driver going near 34 mph. At that speed, the critical stopping distance is 175 feet. Even if we don’t factor in the slowing required for the turn, we can see that there is a minimum dilemma zone created by the 3.5-second yellow if our 50-mph driver gets that yellow when he is between 343 and 175 feet of the intersection. He cannot safely decelerate here, but choosing to proceed puts him in the intersection up to 1.5 seconds after the light turns red.
Jay Beeber has provided an analysis that breaks down this explanation into the components of distance and time, showing the proper calculations to determine the minimum yellow light time for a 50-mph approach. This scientific approach to the question of what the yellow light duration needs to be should be the way our city makes the determination – not the arbitrary approach that was actually used.
Next we will explore another big problem with our camera enforcement.
We Are Paying Too Much For Our Cameras
Our current contract shows we are paying $4,000 per camera intersection approach per month. There are seven total intersections with a total of 10 monitored approaches. That is a whopping $480,000 per year. The hefty fines being collected are paying for this expense and more. The city is left with a net $98,000 in revenue per year from the program.
Why are we paying $4,000 when cities such as Garden Grove are paying $2,900, or Davis paying $2,500, or Solana Beach paying $2,225? I don’t have an answer to this question. Only our city can answer it.
It now must be noted that if the city implements the suggested increase in the yellow-light duration for left turns, under the conditions of our current contract, the financial pinning for this program collapses like a house of cards. At that point, the city would either need to renegotiate the rate so the program pays for itself, decide to subsidize the program, or drop it altogether.
Our council made the right decision to take the contract renewal back from the city manager and put it on an agenda to give time for issues such as these to be addressed. I am grateful to the council acting on my request at the Feb. 11 meeting and am looking forward to it being addressed at the March 25 council meeting. I encourage our council to make one of the following decisions at this meeting:
• Approve an extension of the contract with the provision that the left-turn yellow duration will be increased to 5.0 seconds;
• Approve a renegotiated contract that allows for the city still to make money, with the provision that the yellow-light duration will be increased to 5 seconds;
• Approve the contract with the provision of giving a grace period of 1.5 seconds to left-turn drivers;
• Increase the left-turn yellow duration to 5 seconds and drop the camera program altogether, as there will be few red-light running violations occurring at the city’s intersections. Use live police officers to enforce red-light and other traffic violations.
The bottom line is that our city needs to take reasonable actions to ensure safe streets. Our law enforcement must include punishing those who run red lights through willfulness or negligence. However, to continue to target the left-turn drivers caught in the dilemma zone in an effort to drive the funding of the red-light camera program would be unconscionable and immoral.
James Farley is a Santa Clarita resident.