— Dane Creek

Decoding the I-405 test toll signs

My morning commute takes me down I-405 in Seattle from the SR522 interchange to the SR520 interchange. I have a lot of time to stare at the new I-405 HOT lane signs. After seeing a wide range of test toll codes I’m confident in the following mapping:

Symbol Value
s $
c .
h 0
n 1
d 2
r 3
l 4
t 5
g 7

Here’s all the toll values you’ll see from $0.75 (minimum toll) up to $2.75:

Code Cost
shcgt $0.75
sdchh $2.00
sdcdt $2.25
sdcth $2.50
sdcgt $2.75
slchh $4.00
slcdt $4.25
slcth $4.50
slcgt $4.75

Edit: changed “l” from 1 to 3 based on a tip from @WSDOTGoodToGo. Now I need to figure out what letter is a 1.

Edit: @WSDOTGoodToGo confirmed “l” is a 4.

Edit: After dealing with construction traffic on a Saturday night I’m fairly confident n < r < l. Since L is 4 and the only missing numbers were 1 and 3, that makes n == 1 and r == 3.