A new bill could give Washington drivers some relief on their car-tabs.

A lot of drivers have been hit with sticker shock in the past few weeks, as they got a new look at higher car-tab fees. Sound Transit Three is one big factor pushing up the costs in King, Pierce and Snohomish counties.

Read more about the ST3 tax increase

But another issue that impacts drivers everywhere in the state relates to the value of your vehicle. That's the amount the state uses to figure how much you should pay for your car-tabs.

Senate bill 5851 would require the value of a vehicle to be based on base model Kelly Blue Book values, or National Automobile Dealers Association values, whichever is lower. SB 5851 would also exempt trucks and trailers from motor vehicle excise taxes imposed by a regional transit authority.

State Senator Dino Rossi, R-45th District, sponsored the bill. He said the current system is "completely dishonest. To have a value that isn't market value. Isn't even close to market value."

Right now, the state taxes you based on a somewhat complicated formula.

First, the Department of Licensing uses your car's MSRP, or Manufacturer's Suggested Retail Price. You can call the Department of Licensing and ask them to provide the MSRP they have listed for your vehicle.

Next, find your car's age, or year of service. To do that, take the current calendar year, subtract the model year of your car, then add one year. Once you have the year of service, use this chart to find and apply the corresponding percentage to the vehicle's MSRP. That resulting number is the taxable value of your vehicle, according to the Department of Licensing.

Read more about the math behind your big bill

Earlier this week, KING 5 talked with driver Michael Martinez, who lives in Mukilteo. The Department of Licensing told him the taxable value of his 2010 Range Rover is $36,910. Kelley Blue Book lists the value at about half that amount.

"Everybody would have sold their cars to the state for what the state says their cars were worth, Rep. Rossi said. "So what I decided to do is drop a bill that said it had to be National Auto Dealers Association value or Kelley Blue Book value, whichever is less. Unfortunately right now, that is not what Sound Transit is doing."

The current formula is set by state law and has been in place since 1997. Sound Transit says changing it would be problematic.

"We have a legal commitment to the bond holders saying the bonds would be paid back with interest,," said Geoff Patrick a spokesperson for Sound Transit. "So if there is legislation changing the way in which taxes are collected, it would set up a situation where Sound Transit may not meet legal obligations to bond holders."

He says the legislation would be unconstitutional for that reason.

"It would be unconstitutional, because the constitution respects the obligations made to bond holders."

The Department of Licensing said it's gotten hundreds of calls and complaints regarding the car-tab renewal fees and how they are calculated.