Add lanes, close ramps to speed H-1, study says
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Graphic: Three lanes to four: Easing eastbound H-1 traffic
By Mike Leidemann
Advertiser Transportation Writer
Congestion on H-1 Freeway through urban Honolulu could be cut almost in half by several relatively inexpensive quick fixes, according to a University of Hawai'i study prepared for the state Department of Transportation.
Richard Ambo • The Honolulu Advertiser
The changes include "squeezing" an extra lane of traffic into some areas and closing several on-ramps between Middle Street and Wai'alae Avenue.
Eastbound commuters on H-1 face heavy traffic into town every weekday morning. A study by a UH professor could help ease that gridlock.
None of the changes requires large construction and could be done using existing rights of way, according to Panos Prevedouros, a University of Hawai'i civil-engineering professor who conducted the five-year study under contract with the state.
"No one ever expected this kind of traffic when the freeway was built, but with a little microsurgery we could provide a lot of help," he said.
If approved by the Transportation Department, the changes could be in place within four years and reduce peak-hour delays in the eastbound direction between 37 percent and 48 percent, Prevedouros said. All the work could be done for a few million dollars, as opposed to the hundreds of millions of dollars that new freeway construction typically costs.
"The idea is to maximize the infrastructure we already have in the urban sections of the freeway," said Glenn Yasui, highways administrator for the Transportation Department. "Maybe, there are some things we could improve right away without having to tear down what we have."
The University of Hawai'i report also suggests that a number of other, relatively simple changes could be made to streets near H-1 Freeway in urban Honolulu to relieve congestion. "In sum, the implementation of all these actions could be done at a cost of less than $8 million and are expected to produce a considerable improvement to both freeway and surface street conditions at all times," the report says. Among the suggestions: • Signal optimization and coordination along Vineyard Boulevard. This would help maintain a better traffic flow, which would ease pressures on H-1 Freeway and serve more traffic heading to and from the central business district. • Elimination of left turns from eastbound Vineyard Boulevard at Punchbowl Street. This would improve traffic flow on Vineyard Boulevard in the morning and improve flow on freeway-bound Punchbowl Street in the afternoon. • Eliminate left turns in both directions of Vineyard Boulevard at Liliha Street. This would speed traffic in all directions, while still allowing local drivers to reach their destinations by using other neighborhood streets. • Redesign the intersection and Pali Highway and Vineyard Boulevard to provide two left turn lanes in all directions. By using narrower lane widths, the amount of room for turning cars could be doubled, reducing delays for through traffic and pedestrians. The report also suggests two larger, more expensive projects: • Put a new below-grade ramp at Punchbowl Street and Vineyard Boulevard. An underpass that takes Punchbowl Street traffic underneath Vineyard Boulevard would nearly double the capacity for north-south travel and all but eliminate congestion problems in the area. • Build a new, above-ground ramp that would carry westbound traffic from the two-lane Kapi'olani off-ramp directly to the University of Hawaii-Manoa entry on University Avenue. "Noticeable improvements in efficiency and substantial improvements in safety are expected to be generated by this redesign," the report says.
A final version of the report is expected to be turned over to the state by the end of the month.
Other options for easing traffic
"We still have to review the specific suggestions, but the concept of doing these little fixes here and there definitely makes sense," said Ron Tsuzuki, program manager for the DOT's planning branch.
The biggest improvements would result after the notorious Middle Street merge, where the eastbound Moanalua and H-1 Freeways come together reducing six lanes of traffic to three.
The study proposes creating a fourth lane of traffic between the Likelike Highway and Vineyard Boulevard off-ramps and between the Liliha Street on-ramp and the Pali Highway off-ramp.
That could be done largely by using existing auxiliary lanes and restriping existing freeway lanes, reducing them from 12 feet to 11 feet wide, Prevedouros said.
"The real chokers in the system are at Kalihi and Liliha Streets," he said. "These changes would help a lot."
Even if those are the only improvements made, the total time O'ahu motorists spend stalled in rush-hour traffic would be reduced 37 percent, from 3,777 to 2,306 vehicle hours each day, a standard measurement used in traffic studies.
Additional time savings for eastbound commuters could be realized by closing the Ward Avenue and Pi'ikoi on-ramps from 7 to 8 a.m. and extending an auxiliary lane from the Ward on-ramp to the Punahou Street off-ramp.
Similar but smaller time-savings could be accomplished in the westbound direction by closing several on-ramps, Prevedouros said.
Seven on-ramps are crowded into a one-mile stretch of H-1 west-bound, which was designed and built more than 50 years ago. Typically, new freeway construction spaces on-ramps at least two miles apart to keep traffic on the mainline flowing, Prevedouros said.
Merging traffic from on-ramps slows freeway speeds substantially, especially when there is a heavy entering volume, adjacent entry and exit points and limited merging distances, he said.
The biggest benefits for west-bound drivers would come from closing the Lunalilo Street on-ramp during peak morning hours. At that site, about 3,200 cars per hour fight one another to get on and off the freeway, creating a shock wave of delay that can stretch back past University Avenue.
"Just closing that on-ramp alone could reduce delays about 35 percent," Prevedouros estimates.
Drivers wanting to get on the freeway would be directed to the Vineyard Boulevard off-ramp and then to the Punchbowl Street on-ramp or the access lane to Pali Highway.
In the afternoon and weekend bottleneck hours, traffic could be better managed in the Lunalilo trouble spot with an "intelligent, demand response method," such as ramp-metering, Prevedouros said.
Transportation officials experimented several years ago with temporary closing of the Lunalilo street on-ramp using plastic cones and found there was at least a 15 percent reduction in freeway congestion, Yasui said.
"We're definitely looking at doing something like that again using a more permanent type of barrier," Yasui said.
The UH report also recommends freeway changes between the Vineyard Boulevard on-ramp and the Likelike Highway on-ramp, including improving the Alexander Street on-ramp and providing afternoon ramp metering.
In general, though, ramp metering, in which a timed traffic signal controls access to the freeway, won't work in urban Honolulu because vehicle volumes are too high and space for cars waiting in line is too short, Prevedouros said.
The closure of any on-ramp is likely to create some opposition from drivers trying to get on the freeway and neighborhood residents who will see some increased traffic.
"It's never a total win-win situation," Prevedouros said. "There's going to be a few minutes delay for a few vehicles trying to get on the freeway, but you save a minute or two for thousands of others who are already there."
Narrowing the width of lanes would require approval of the federal government, which sets minimum standards for interstate freeways.
"It does require an exception of federal standards, but it's been done in other places," said Abe Wong, head of the Federal Highway Administration in Hawai'i. "If they can squeeze more traffic in and do it safely, then it's something we'd review and take action on."
Reach Mike Leidemann at 525-5460 or mleidemann@honoluluadvertiser.com.
