Slow Down: Grading’s on a Curve

Take it easy, lead foot.

That’s the message Caltrans engineers are offering beach-bound commuters today as motorists inaugurate a newly constructed, $6.5-million freeway link between the Corona del Mar and Costa Mesa freeways.

The tight-turning loop is expected to shave as much as 15 minutes off the average trip to the beach. But engineers warned drivers to mind the 25-mph speed limit or risk a seriously spoiled Labor Day weekend.

“Just go slow. We don’t want to see any skid marks,” Caltrans Construction Engineer Dipak Roy said.

The freeway connector is the first element of an $86.7-million package of road improvements slated for the bustling freeway interchange in the shadow of South Coast Plaza. The work, which is scheduled to be completed in 2003, is intended to improve traffic flow by adding traffic lanes and access ramps.

The new ramp includes a hairpin curve that requires motorists to significantly slow down. Caltrans has placed three speed warning signs on the approach to the loop, which spans a drainage basin and borders a housing development.

Caltrans officials maintain that the loop is safe and offers motorists full visibility so that they are not taken by surprise by the curve’s shape or by stacked traffic.

“The more you see, the better off you are,” said Barry Rabbitt, a Caltrans construction chief. “There’s total visibility here.”

The reason for the design, officials said, is that the connector had to be built on a small plot of land that was further constricted by freeway pylons.

Caltrans and Orange County Transportation Authority officials say the loop meets all standards for the Federal Highway Administration and state highway design for speed, banking and size.

Traffic curves are classified according to their radius, which is the distance from all points along a curve to an equally distant imaginary point, or focus. The Corona del Mar-Costa Mesa freeway connection has a radius of 51.5 meters, according to Caltrans. The smallest curve allowed under state standards has a 40-meter radius. Curve speed limits are prescribed in the state standards according to the curve’s radius, officials said.

Comparable 25-mph loops can be found on the northbound Orange Freeway to the westbound Riverside Freeway; the Artesia Freeway to the San Gabriel River Freeway north and south and at the Orange Crush interchange.

The new link, which joins the northbound Corona del Mar Freeway to the southbound Costa Mesa Freeway, will funnel as many as 20,000 cars and trucks a day to Orange County’s coastline, officials said.

When the interchange was constructed in 1978, officials believed there was little demand for such a link, and none was built. Frustrated motorists were forced to take surface streets in Costa Mesa to make the connection from parts of South County to Newport Beach.

The larger improvement project will modify access ramps at the San Diego and Corona del Mar freeways interchange to reduce confusion. Four new traffic lanes will also be built. Work is currently being done on a $3.9-million auxiliary lane for entering and exiting the San Diego Freeway between Harbor Boulevard and Euclid Street. To accommodate the new lane, a bridge over the Santa Ana River will be widened.

The last segment of work will involve the construction of $61.5 million worth of new and expanded access ramps on the San Diego Freeway and three lanes and a ramp on the Corona del Mar Freeway for $14.8 million.

The interchange currently handles 280,000 cars a day and is expected to accommodate 340,000 vehicles by 2020.