See Is the IBR setting up another transit failure?“C-TRAN offers the only transit service across the Columbia River, as there hasn’t been enough demand for TriMet to offer service as well. C-TRAN’s ridership to Portland peaked in 2016 and has been in decline ever since. 
Average weekday ridership on C-TRAN express bus routes to Portland:
2016 – 3,040
2017 – 2,874
2018 – 2,844
2019 – 2,892
2020 – 971
C-TRAN experienced a 61 percent drop in passenger boardings on the express bus system over the past two years.

The flexibility of BRT (or express bus) to serve different communities far exceeds the ability of light rail, which is limited by where you put the tracks down…

Transportation architect Kevin Peterson has pointed out that one vehicle lane can handle about 1,800 vehicles an hour. If that’s the case, it would seem all those BRT double-articulated buses could easily travel in a vehicle lane, alongside cars and trucks and freight. They would only occupy at most 10 percent of the vehicle capacity one lane provides.Why not allow other vehicles to use that lane when buses are not present?”
****************************************************************************************************Today, CTRAN buses and vans on the 3 thru lanes on the I-5 bridge share the road with other traffic like freight, commuters, commercial vehicles. Buses are flexible in route and vehicle size ( 40 ft bus ,60 ft articulated bus, or smaller bus/van).

So far, the IBR has not informed legislators or the public what data and assumptions are being used in the secret models to predict an unrealistic 10-fold increase in the use of public transit on I-5. It appears to be “strategic misrepresentation’.
The public has not been informed yet about updated estimated costs of light rail on an I-5 Replacement Bridge.
Reporter John Ley has noted “TriMet has spent $200 million to $400 million per mile to create new light rail lines.”
Old CRC data estimated ~ $ 850 Million for gold plated light rail, to serve less than 2% of the trips across the bridge.

Roads for all traffic, including affordable buses VS. gold plated light rail for the 2%