Failing Grades : Major Intersections Can’t Pass Muster or Traffic in Rush Hour

A lot of San Fernando Valley intersections have been getting F’s in traffic school lately.

As with students, an F-graded intersection has flunked and needs remedial work. It’s not a grade that a traffic engineer, or motorist, wants to see on an intersection’s report card.

In response to widespread demand for slower growth, Los Angeles city planners in recent years have been taking a closer look at streets and traffic. In particular, they have focused on intersections--the choke point of surface streets.

Using nationally recognized criteria, planners in past year have graded 23 intersections on Ventura Boulevard and 17 in Warner Center, the fast-growing Woodland Hills commercial area.

It will be no surprise to exasperated motorists that many intersections flunked.

Based on standards set by the National Academy of Sciences, eight have been given F’s--a planner’s designation for gridlock--and 10 have gotten E’s, which is less than full gridlock but still a grade no self-respecting crossing would want.

Along Ventura Boulevard, F’s were handed out where it crosses Lankershim Boulevard, Coldwater Canyon Avenue, Sepulveda Boulevard, White Oak Avenue and Woodlake Avenue.

In Warner Center, where the honking of gridlocked cars competes with the sounds of the construction of high-rise buildings, the F-rated intersections are Topanga Canyon and Victory boulevards, Canoga Avenue and Vanowen Street, and De Soto Avenue and Vanowen.

In coming years, city planners intend to use the intersection data to determine whether, and how much, a developer should pay for such things as new left- and right-turn lanes or new traffic signals to offset congestion caused by a development.

The National Academy of Sciences describes an F-rated crossing as one that, during peak commuting hours, operates beyond its design capacity, with vehicles backed up at the intersection sometimes blocking other intersections.

1,500 Cars Per Lane Per Hour

Traffic engineers consider a roadway’s capacity to be 1,500 cars per lane per hour, said T. K. Prime, an engineer with the Los Angeles City Department of Transportation.

A road with one lane in each direction and a center lane for left turns has a design capacity of 4,500 cars an hour.

At an intersection where a stoplight is red half the time, the capacity is cut in half, to 2,250 cars an hour.

The addition of a turn lane, with capacity for 1,500 cars more an hour, “often dramatically improves an intersection, at least until the traffic builds up again,” Prime said.

An E-rated intersection is operating at capacity and is significantly less congested than an F-rated one. Yet, during peak commuting hours, motorists must wait through several signal changes to get through an E intersection.

Even a D-rated intersection forces motorists to endure substantial waits during the peak travel periods. However, unlike E and F intersections, a D-rated crossing has enough periods of lighter traffic, even during peak hours, to clear out long lines.

At the heaviest travel times, C-rated crossings usually have some backing up in left-turn lanes and, occasionally, motorists are forced to wait more than one signal to get through the intersection.

A B-rated crossing is free-flowing throughout peak periods, but sometimes one or more approach streets are at capacity. An A-rated intersection permits motorists to flow freely at high speeds.

Of course, even the worst intersections have their good times. Ratings, taken during peak commuting hours, almost always represent the worst-case situations.

Prime said the evening rush-hour rating is considered more important than the morning one “because shoppers and people running errands are more likely to be on the street at the same time as commuters in the evening, so that is usually, but not always, the worst-case situation.”

If funds are available only to rate morning or evening, planners always choose the evening, he said. On Ventura Boulevard, traffic has been metered for both morning and evening peak hours.

In Warner Center, however, engineers have set up traffic counters, the basic tool for gathering the data, only in the evening.

The results on Ventura Boulevard illustrate that there is no guarantee that morning is better than evening. Of the 23 Ventura intersections rated for both morning and evening traffic, four were worse in the morning than in the evening, whereas five were the same.

Proving that the difference can be dramatic, the intersection of Woodlake and Ventura in Woodland Hills got an A in the morning and an F in the evening.

Late-Day Congestion

City traffic engineers say that motorists seeking to get on the Ventura Freeway’s westbound on-ramp at Woodlake are the cause of the late-day congestion.

City planners predict that residents are going to hear a lot about intersection ratings in coming years.

For one thing, leaders of Los Angeles’ growing slow-growth movement are likely to find intersection ratings a handy tool in opposing developments.

And intersection grades are the “essential raw data needed to start to improve a congested area,” said City Planner Mark Woersching, who is overseeing the Warner Center and Ventura Boulevard studies.

Planners also say the continuing shortage of road-building funds has led to a widespread belief in city government that developers should be required to pay for road and intersection improvements to offset congestion they cause.

Because of this change in attitude, the Los Angeles City Council, which has a new sympathy for slowing growth, has in the last two years adopted a series of moratoriums throughout the city.

Both the Ventura Boulevard and Warner Center traffic studies resulted from moratoriums aimed at temporarily halting the construction of large buildings while new development rules are drafted.

Over the next few years, both areas are expected to be rezoned as a result of the rules being drawn up.

And both moratoriums were accompanied by interim ordinances allowing the Department of Transportation to levy fees on developers to alleviate increased traffic congestion.

RATING THE INTERSECTIONS

Below are nationally recognized standards for intersections, as listed in the Highway Capacity Manual of the National Academy of Sciences.

A -- Light traffic, flowing freely and at high speed.

B -- Free flowing, but some approach streets are occasionally at capacity. Motorists at times feel restricted.

C -- Occasionally, motorists forced to wait more than one red signal to pass through intersection. Some backing up behind turning vehicles.

D -- Substantial delays during busiest portions of peak periods, but there are enough cycles with lighter traffic to clean out backup.

E -- Long queues to enter intersection, with motorists forced to wait through several signals during busiest periods. F -- Long queues and delays are common. Backup from one signal at times blocks another, and vehicles from nearby driveways or cross streets sometimes prevent vehicles from leaving the intersection.

VENTURA BLVD. CORRIDOR

Morning and late afternoon peak hours

Intersection of A.M. P.M. Ventura Bl. & WOODLAKE AVE. A F & FALLBROOK AVE. B D & SHOUP AVE. B D & TOPANGA CYN. BLVD. C C & CANOGA AVE. C D & DE SOTO AVE. E B & WINNETKA AVE. E D & TAMPA AVE. D C & RESEDA BLVD. B D & LINDLEY AVE. D B & WHITE OAK AVE. F C & BALBOA BLVD. E C & HAYVENHURST AVE. E E & SHERMAN OAKS AVE. D B & SEPULVEDA BLVD. F F & VAN NUYS BLVD. C E & BEVERLY BLVD. B D & WOODMAN AVE. C C & COLDWATER CYN. AVE. E F & LAUREL CYN. BLVD. C E & TUJUNGA AVE. A A & VINELAND BLVD. D E & LANKERSHIM BLVD. F F

WARNER CENTER AREA

Late afternoon peak hour*

INTERSECTION P.M. Top. Cyn. Bl. & Vanowen St. E & Victory Bl. F & Erwin St. C & Oxnard St. E & Burbank Bl. D Canoga Ave. & Vanowen St. F & Victory Bl. D & Burbank Bl. C De Soto Ave. & Vanowen St. F & Victory Bl. E & Vent. Fwy. D Eastward ramps & Vent. Fwy. B Westward ramps & Oxnard St. C Canoga Ave. & Erwin St. A & Oxnard St. A & Vent. Fwy. B Eastward ramp & Vent. Fwy. B Westward off-ramp