4/8/2022 #kihei #highschool #roundabout #underpass

What is the difference between a signaled intersection and a roundabout?

  • In a signaled intersection, all through traffic and left turns in one or more directions are halted while traffic goes forward in another direction
  • In a roundabout, traffic flows continuously from and to all directions

Why would you want traffic to flow continuously instead of stopping and starting?

  • There are a lot of people who need to get to or from South Kihei every day. Increasing their daily commute time by an hour or more daily because of flow interruptions at an additional intersection will make their lives more unpleasant and cause some to miss appointments or arrive late to work.
  • There will be many more cars on the road with students going to and from the high school, causing even more congestion, especially if they have to stop for another traffic light.
  • Long periods of idling and frequent starts and stops results in greater vehicle exhausts for those not driving an electric vehicle – bad for air quality and the climate.

Won’t traffic slow down compared to a road with no roundabouts and no signaled intersections?

  • Yes, the speed is expected to be 20-25 miles per hour once the roundabout is in place.
  • The number of vehicles able to pass through per hour will be higher than for a signaled intersection because traffic will flow continuously instead of regularly coming to a complete stop.
  • The lower speed will contribute to less accidents, less injuries and much fewer deaths than a signaled intersection.

Can a normal driver navigate a roundabout?

  • The skills required to navigate a multi-lane roundabout are:
    • Merge into traffic
    • Be able to change lanes
    • Be able to turn right
  • The skills required for a signaled intersection such as the one at Piilani Highway and Piikea, are:
    • Merge into traffic
    • Be able to change lanes
    • Be able to turn right
    • Be able to turn left
    • React appropriately to changes in traffic lights
  • It is easier to merge into a roundabout then into an intersection because you can see the whole field at one time (if there are any vehicles in the roundabout), where it can be difficult to see all coming traffic at an intersection.

Are there really less accidents and injuries in a multi-lane roundabout than in a signaled intersection?

  • Yes. For large multi-lane intersections converted to roundabouts, conversions have resulted in a 29% reduction of collisions and a 31% reduction of injuries. For all roundabouts (single and multi-lane), the reductions are 37% and 51%.

Are you making this up?

  • No, there have been many studies the past ten years comparing accident rates at intersections with comparable roundabouts, including intersections converted to roundabouts. 
  • The US Department of Transportation has published an extensive summary of studies done and results found around the safety of roundabouts, including multi-lane roundabouts:
    It is well worth reading.

I lived in New Jersey and their roundabouts don’t work; some have been removed; how will ours be different?

  • 20th century roundabouts had an entirely different and ineffective design. The vast rollout of roundabouts in the US and Europe since then has been very successful, as shown in the Department of Transportation report above.

Does a roundabout cause more traffic?

  • No. The amount of traffic depends on the number of vehicles passing through within a time frame. A roundabout reduces congestion by allowing for a steady flow, but it doesn’t change the number of vehicles on the road during a day.

Is a roundabout safe for school children to cross?

  • A roundabout is safer to cross than a signaled intersection (if there are stop lights that can be triggered by the children), but Kihei Community Association feels there are still risks, including that some kids will try to race across without waiting for traffic. The County’s “Vision Zero” goal is for no one to die in traffic, not just a smaller number than before.
  • However, stop lights would to a large extent prevent a continuous flow of traffic, one of the main benefits of a roundabout.
  • Children should not have to cross the highway, they should have a grade separated crossing (GSC) as required by the State Land Use Commission for the school.

What is a grade separated crossing (GSC)?

  • A grade separated crossing is one where pedestrians and bicyclists do not cross on the highway at all: either an underpass or an overpass.

Why is an underpass better than an overpass for the high school crossing?

  • The  Americans with Disabilities Act (ADA) mandates that a public crossing such as this one have a maximum grade of 5%, meaning very long ramps and a total length of 300-400 feet. Studies of comparable overpasses, including one on O?ahu, show that school age children will not use an overpass if it adds that much distance to their trip but will instead try to cross the highway at a closer spot to where they are coming from.
  • An overpass is at least three times more expensive than an underpass.

Is it realistic to build an underpass?

  • Yes, the very wide Waipuilani gulch crosses under the highway 100 feet from the school boundary.
  • It has ten feet of clearance, enough for a safe, three foot elevated walkway with a guard rail along the north side.

Could you use the underpass in a severe storm?

  • No, when there is a severe storm with flooding as on December 5, 2021, the schools close and there is no need to use the underpass to get to school. However, with the proposed elevated walkway, the underpass would have been usable also on December 5, 2021.
  • If the school is still open in a 100-year storm, the students would need to cross at the roundabout or get a ride. That is similar to the case for most underpasses in the world, many of which have trails along a river under a road, e.g.:

What if the roundabout is built but not the underpass?

  • When the Department of Education (DOE) insisted almost ten years ago on putting the school mauka of the highway, the state Land Use Commission (LUC)  put a requirement in place that the school could not be opened without a grade separated crossing (see above for the meaning of a grade separated crossing) for the students.
  • The state Department  of Transportation, represented by Ed Sniffen, has tried repeatedly to get the LUC to drop the requirement but the LUC has unanimously rejected the request, considering the safety of the school children to be an important criteria for the school’s opening.
  • The county Department of Planning will not grant a permit of occupancy until the grade separated crossing has been provided.
  • But the Department of Transportation is continuing to ignore the requirement. Those who would like to see the Department fulfill its obligation to provide a safe crossing for the children should let them know that is the case.

Where can I read more about the pros and cons of different options for students to get to the new high school?

Ask Deputy Director of Highways Ed Sniffen of the Hawaii Department of Transportation to provide an underpass for the safety of the school children, as required by the LUC condition: