Monday, November 9, 2015

Why is it hard to see lanes on Snoqualmie Pass at night and in the rain?

By Summer Derrey

It's not your vision. Sometimes, it's difficult to see the lane markings on I-90 over Snoqualmie Pass.

The pavement markings on I-90 over Snoqualmie Pass have glass beads, providing reflectivity and making them bright in headlights. But rain is a significant problem even with new paint. Rain covers the glass beads and reduces reflectivity so the lines are not as bright and visible.

We have tried many alternative striping products that are very expensive and or time consuming to apply. If we find something new, we are willing to test it, but we have not found a product durable enough to withstand the traffic and snow removal equipment. The most durable products lose reflectivity very quickly providing limited guidance in the dark, and especially when wet.

We've tried other ways to make the lane markings visible on I-90. We installed Raised Recessed Pavement Markers (RRPM's) on I-90 from North Bend to Cle Elum.  The markers sit in slots below the level of the pavement to protect them from studded tires, chains and snow removal equipment, but are less visible when the slots fill with rain or snow.

Stripes and recessed pavement markers delineate lanes.

Last year, we installed more than 4,600 LED pavement markers in a seven mile section of I-90 near the summit in both directions. It's a test to see if these markers help drivers at night and in inclement weather, and if they can withstand the punishing conditions on Snoqualmie Pass. Since they are solar powered, grey days sometimes prevent the lights from shining all night.
We are monitoring LED lights for the next several years to see how well they hold up in harsh mountain pass conditions.

Glare screens were installed several years ago on the barrier from Hyak to Easton to reduce blinding headlights. While this does not specifically address lane markings, it is part of our efforts to improve visibility on I-90.

Overhead lighting is used at key locations, primary on and off ramps.  The overhead lighting in the chain up and off areas is for the safety of those chaining up on the side of the road in adverse weather conditions.

The other significant factor for visibility is traffic volume. More vehicles, more glare and more road spray makes it difficult to see.

We are still looking for cost-effective solutions to make lane markings last longer and easier to see on Snoqualmie Pass. Until then, we will reapply paint at least twice a year and when needed as conditions allow.

Our best advice to travelers is don't drive too fast for the conditions.  Adjust your speed when difficult conditions limit visibility.

1 comment:

Jeff Gray said...

Well, my headlights won't be adding to the illumination. Since the implementation of the Extortion Toll Lanes has turned 405 into a parking lot, it would take me three hours just to GET to I-90.

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