Low transit fares may seem a great bargain for riders, unless they’re so low they help to drive up demand beyond a service’s capacity to deliver.

This is especially true in the case of TheHandi-Van, the city’s on-demand shuttle intended to serve those with disabilities who can’t use TheBus — although some shuttle riders, in fact, do have the choice.

But as long as the city’s “paratransit” fares — $2 — remain suppressed below those charged to bus riders, there’s scant reason why anyone qualified to ride either would choose the bus over a door-to-door service.

As a result, city officials have said, Handi-Van service, as heavily subsidized as it is, cannot keep up with demand. This is despite its somewhat newer and enlarged fleet, which has whittled down but not eliminated the challenge of keeping vans maintained and available for use.

This must change. If the Handi-Van program is to function as a viable transportation mode for Oahu’s disabled and infirm, it must be made more sustainable. And the city should consider ways of enlisting the capacity of ride-hailing networks such as Uber and Lyft, as well as conventional taxis, to fill in the gaps.

The shortcomings of the system are a well-established problem. More than a year ago, the city auditor released a report noting that the last fare increase took place in 2001. It also chronicled the fleet increase and the effort to supplement with taxis — as well as the ongoing deficiencies.

As a result, according to the audit, on-time performance had declined 5 percent over the preceding three years, with excessive trip times and difficulties meeting the demand.

Then at the end of June, the city Department of Transportation Services released its Paratransit Growth Management Study. That report concluded that, between 2001 and 2008, demand for services has risen annually by 3-5 percent. That rate accelerated starting in 2009, with the number of trips increasing by 5-6 percent each year through 2015.

This issue is specific to Handi-Van services, according to the study, because trips provided on TheBus rose slightly since 2009 and then declined and leveled off.

Jon Nouchi, deputy director of DTS, said bus fares have gone up five times since the last Handi-Van increase of 2001. Now it’s cheaper to ride paratransit than the city bus, which is not as it should be.

Estimates of the actual cost of the rides vary, but $45 per trip is at the low end. The study made a reasonable recommendation, at a minimum: raising the fare by 50 cents until it reaches $4.

Nouchi said that Handi-Van drivers do have to qualify to ride paratransit by undergoing an eligibility evaluation, and people do get rejected.

But, he said, there are a number of riders who qualify for Handi-Van service but remain capable of using TheBus. These people need to be encouraged to ride the bus more often, and raising the paratransit fare is essential to that aim.

The city also needs to consider alternative strategies to manage the demand. Taxis are employed, but they are more suited to short trips, Nouchi said, because the city subsidy also must cover tariffs charged by distance.

And for that reason, the city also should explore ride-hailing services such as Uber and Lyft, which are piloting specialized services for the disabled.

Some Honolulu officials have had reservations about ride-hailing, but it would be wise for the city to explore whether the services — Lyft’s Access Mode and Uber’s uberWAV and uberASSIST pilot programs — could help fill the gap on Oahu.

Finally, Nouchi said, it’s wrong to assume that the disabled lack the ability to pay a fairer share of their own transportation costs.

The sooner a more equitable fare structure can be approved, the sooner it can lead to more sustainable transit for all.