Lots of traffic, little data
Los Angeles’ traffic signal system is the envy of traffic planners around the world, recording millions of cars each year as they pass over sensors embedded in city streets.
The data beep and shine on screens in a state-of-the-art traffic control center that looks like something out of a science fiction movie. The information -- Wilshire Boulevard jammed in Westwood, Broadway wide-open through downtown -- is used to adjust the timing of traffic lights, easing the flow of vehicles through the city’s busy streets. The data are instantly placed on the Internet, available to commuters and traffic reporters.
But although the sensors and computers collect massive amounts of data about traffic patterns and congestion, they do little to help engineers plan for the city’s growing transportation needs -- or determine how development is affecting traffic.
That’s because the city does not save the information for more than a few days, using it only to direct traffic in real time by adjusting the speed at which lights turn from green to amber to red.
Because the information is discarded, it cannot be used to determine over time where traffic is increasing -- or by how much.
In fact, city officials said they don’t have traffic counts for some of the city’s busiest intersections -- and can’t say how much congestion has increased over the years
The lack of traffic data is becoming more of a vexing issue at City Hall and in L.A. neighborhoods, especially in the midst of a building boom that has increased both residential and office development.
And it will probably be on the agenda for the new head of the Los Angeles Department of Transportation, Rita Robinson, who until last week was the city’s sanitation director. The former chief, Gloria Jeff, was fired by Mayor Antonio Villaraigosa on Friday. Jeff’s ouster came after months of grumbling that the department was slow in making improvements aimed at lessening worsening street congestion.
Many at City Hall believe getting better traffic data is crucial.
“It’s appalling,” said Councilwoman Wendy Greuel. The chronic lack of information makes it impossible to determine “where density should go and where it shouldn’t go.”
Over the last decade, several huge developments have been built, including the Hollywood & Highland shopping center, the ArcLight movie theater and the W Hotel complex at Hollywood and Vine, a mixed-used project now rising at the famous intersection.
But city officials said that they don’t know how much the boom has affected traffic, because there is little historical data.
City codes require developers to produce a traffic study before building a new project, and city traffic engineers conduct a count of surrounding streets at that time.
But the developer and city traffic planners generally are not required to follow that up with updated counts after the project goes in.
As a result, planners might know how much traffic an area had before a development was built, but not afterward.
“One of the challenges that the city of Los Angeles has had over the years is that they have reduced the staffing that’s been available to do data collection,” said Jeff in an interview before her dismissal. Although Jeff was politic in her description of the problem, an aide said that the former Michigan official had been shocked when she arrived two years ago at how little information Los Angeles gathered about traffic.
Bill Reichmuth, transportation chairman for the American Public Works Assn. and a top traffic planner in Monterey, Calif., said planners in built-out cities like Los Angeles need such historical data to decide how large redevelopment projects should be, and where they should go.
“If you don’t have it, you’re hamstrung,” Reichmuth said. “Without that data, you’ve got no way to make those kinds of assessments.”
City Council President Eric Garcetti said it would cost about $1 million to start organizing and archiving data from the city’s traffic control system.
Jeff said the transportation department could begin installing a system to do that in July, but it would not be up and running for the entire city until 2011. The job will now fall to Robinson, who was appointed by Villaraigosa on Friday.
Some traffic agencies are significantly ahead of L.A.
Caltrans has long conducted intricate traffic counts along state highways and freeways. And several other California cities have found ways to do it.
San Francisco is implementing a computerized system for counting cars on its most congested and important streets and retaining the data. The city does regular counts of most of its arterial streets at least every seven years, and sometimes more frequently.
Every street in San Diego that carries 3,000 vehicles per day is counted at least every three years, said a city spokesman, Eric Simon. San Jose does a yearly traffic count at its busiest intersections, and Long Beach does so roughly every five years.
Ruth Smith, president of the Southern California chapter of the Institute of Transportation Engineers, said that cities vary in the degree to which they keep historical data. A former traffic official in Santa Ana, where engineers do keep a historical record of busy streets, Smith said counting vehicles can cost up to $250 per day per intersection.
Los Angeles does collect basic traffic data at a limited number of intersections, but Jeff and others said the information is not of the type that can provide a thorough picture of the city’s traffic and how it has changed over time.
For example, for decades the city has collected information on the number of cars that cross certain community boundaries as a way of figuring out roughly how much traffic is entering and leaving parts of Los Angeles.
But the streets were chosen for their geographical locations, not their level of congestion or their importance in moving traffic.
These boundaries, called “screen lines,” form a widely spaced grid. One section, for example, is formed roughly by Western Avenue to the east, La Cienega Boulevard to the west, Mulholland Drive to the north and Beverly Boulevard to the south.
Once a year, the city counts the cars that cross these streets, and the data provide a basic sense of how traffic flows into and out of the city. But the information is not meant to show -- and in fact does not include -- how many cars are really inching along arterials or driving on neighborhood streets.
“They’re simply an indicator of the volume of traffic going in and out,” said Jeff. “We draw a series of lines around the city to get a feeling for the volume of traffic crossing into the city. . . . It is not a comprehensive look, nor is it intended to be a comprehensive look at different streets.”
A planner seeking information on Hollywood, for example, would be limited under the screen line system to traffic counts at Western Avenue, far to the east of most of the major development, or Beverly Boulevard, significantly south of it. Hollywood Boulevard, which has seen huge amounts of construction over the last 10 years, is not a focus of the screen line counts.
The city also does another form of traffic counting: the Congestion Management Program. As part of the program, planners count vehicles at 47 intersections around the city every year. The information is used both in assessing air pollution from cars and in regional planning.
But like the screen line locations, the intersections in the management program are not chosen for their local importance or usage levels, said Brad McAllester, executive director of long-range planning for the Metropolitan Transportation Authority.
Instead, McAllester said, the intersections studied in the program were chosen for their importance in county and regional planning -- not because of their role in moving cars within Los Angeles.
“The spacing was designed to give us a picture at the countywide level, not the neighborhood level,” McAllester said.
In addition, neither program measures traffic along the length of the city’s streets, but simply looks at intersections.
As a result of all these considerations, both McAllester and Jeff said, planners seeking information on the most crowded intersections in Los Angeles, or whether certain streets have become more crowded as a result of development, simply cannot do so with the information currently available.
John Fisher, assistant general manager of L.A.'s transportation department, said that, taken as a whole, the information collected by the city provides a useful picture of current and historical conditions in some areas. For example, he said, the city for decades has conducted a separate count of traffic downtown every five years, and has kept information back to 1924.
But other city officials say they keenly feel the lack of traffic data at the neighborhood level.
“This City Council feels strongly that it’s time to link together traffic studies and neighborhood planning,” Garcetti said, “and to have a neighborhood focus on top of the traditional regional focus on traffic patterns.”