The Colorado Department of Transportation has a $9 billion backlog of major infrastructure projects it needs to complete. These include upgrades on Interstates 25 and 70 and other major corridors that, as the state’s population grows, will bear ever-increasing demands.

The state has not succeeded in keeping up with costs. A fair measure of blame belongs to elected leaders, who failed to adequately fund this essential responsibility of state government, though he predicament is also due to the diminished capacity of Colorado’s traditional source of transportation infrastructure funding — gas taxes and registration fees — to supply enough money.

Blame aside, most commuters and travelers can attest to the need in Colorado for urgent road and bridge improvements. That’s why the ballot this year contains not one but two initiatives — Proposition 109 and Proposition 110 — that offer solutions. Only Proposition 110 merits voter approval.

The initiatives propose radically different approaches to paying for transportation projects. Proposition 109, also know as “Fix Our Damn Roads,” asks for the state to bond for $3.5 billion, which would be repaid from money already in state coffers. Proposition 110, also known as “Let’s Go Colorado,” asks for 20 years worth of a new state sales tax of 0.62 percent, which could raise an estimated $20 billion, and the proposition also would allow the state to bond for $6 billion up front, which would be repaid through the new sales tax.

The initiatives pose a simple question: To tax or not to tax? If that were all there was to it, the choice would be easy, because no one likes taxes, but it’s not that simple, because neither does anyone like failing infrastructure.

Proposition 110 aspires to go much further toward clearing the transportation-project backlog, and it proposes a multi-tiered distribution scheme: 45 percent of revenue would go toward state projects and 40 percent would go to cities and counties for local projects — this would allow a mix of overarching projects and those that individual communities select according to local needs. The remaining 15 percent of revenue would be earmarked for multimodal projects, such as bike and pedestrian paths.

Proposition 110 treats the state’s transportation infrastructure needs as an integrated problem and assumes that what’s directly good for one part of the state is indirectly good for every other. If a highway is widened in the mountains, Front Range residents benefit, not just when they happen to drive that stretch but also because a state whose infrastructure is well-maintained is one that’s more attractive to visitors, new residents and businesses. That’s why many officials in and around Boulder County have endorsed Proposition 110, even though it’s expected that the area would experience a net outflow of 110 revenue. Local officials calculate that a better Colorado economy overall benefits the local economy in particular.

Proposition 109’s obvious advantage is that is promises funding without a new tax. But this does not outweigh the measure’s shortcomings. The money it would raise would not cover anywhere near CDOT’s full backlog, and none of the projects it would fund would be subject to local selection or control. The projects 109 would fund are limited to highways, and the measure would do nothing to support development of multimodal options. The money borrowed under 109 would be repaid from existing state funds, meaning that debt would compete with other government responsibilities, such as education and health care. Furthermore, without a dedicated source of revenue, as is envisioned under Proposition 110, bonding is more expensive, and the reliability of funds are less certain, especially in the event of an economic downturn.

The state highway projects that would be funded under either initiative have already been identified, but opponents of Proposition 110 argue that the measure would set aside vast amounts of money for local projects that, at this point, are a mystery. This is a fair criticism. Advocates of the measure might counter that many local governments, just like the state, have a backlog of specific projects they’d be empowered to complete with 110 funding, and this is certainly true in a growing area like Boulder County. But Proposition 110 is disquietingly open-ended on what local money would actually pay for. It would be a betrayal were Boulder-area officials to squander 110 funds on ineffective alternative transportation schemes instead of road projects that reward drivers with real improvements.

Another common criticism of Proposition 110 is that it trades the gas tax for a new sales tax as a primary source of transportation-infrastructure funding. The gas tax matches responsibility for road maintenance with actual users of the roads, whereas a sales tax is inherently regressive, and it forces even people who don’t own cars to pay for roads.

The gas tax in Colorado is 22 cents a gallon and was last raised in 1991. The following year, Colorado voters passed the Taxpayer’s Bill of Rights, or TABOR, which ever since has prevented lawmakers from simply raising taxes, including the gas tax. But raising the gas tax to catch up on transportation projects is a nonstarter. A report this year from 9News concluded that, to meet current needs, the state would have to raise the gas tax to 56.9 cents per gallon — a 156 percent increase — which would make Colorado’s gas tax the highest in the nation. Plus, the gas tax is much less potent than in was 1991, as vehicles become increasingly fuel efficient.

Proponents of Proposition 110 know that Coloradans are infamous for rejecting big tax asks, and they’ve tried to soften the impact of the measure with the tagline “6 cents on a $10 purchase.” Doesn’t sound like much. But taxes add up. The sales tax in Boulder, for example, is 8.845 percent. Proposition 110 would make it 9.465 percent -— close to 10 percent, or a dollar on a $10 purchase.

That’s hard to swallow, and it inspires deep frustration with Colorado lawmakers. It might be true that the gas tax is ill-equipped, at least on its own, to adequately provide for statewide transportation projects, but that doesn’t absolve the legislature from performing the fundamental duty of maintaining roads and bridges. Lawmakers’ approach — let the ailment fester until it’s an emergency — has understandably engendered some resentment among constituents.

Colorado voters should reject Proposition 109, because it doesn’t meet the challenge facing the state, and it could compromise the availability of funds for education, health care and other state responsibilities. And voters should approve Proposition 110, not because it’s the smartest public policy, but to help safeguard the state’s continued prosperity.

Quentin Young, for the editorial board, quentin@dailycamera.com, @qpyoungnews.