It’s happened to everyone who rides the bus. The person in front spends an eternity fumbling for coins, counting, recounting, arguing with the driver over the fare, then pulls out a huge banknote and wants change. That common, infuriating scene may be about to pass into the realm of bad memories, thanks to a new Israeli app.

It’s pretty simple. HopOn lets passengers just climb aboard, paying their fares through their cellphones. Not only will passengers who want to save time appreciate it, so will the bus companies, saving money by not having to print out receipts and saving gas because waiting times are shorter, said David Mezuman, HopOn’s CEO. The system is in the pilot project stage.

“We use ultrasonic sound to validate passenger fares with payments made by the user’s credit card, registered to the app during the signup process,” said Mezuman, who built the app with partner Ofer Sinai. “The validation is done with a small device that we provide, which is placed at the entrance of the bus, and deducts payment from the credit card as a passenger boards. The driver does nothing except look at the indicator to ensure that the passenger has paid, and the passenger does nothing except walk on the bus.”

HopOn is especially useful in a place like Israel, where drivers make change for passengers. While “considerate” passengers pay their fare with exact change, there is always going to be a passenger who tries to pay a 10 shekel fare with a 200 shekel bill — forcing everyone behind them to cool their heels while the driver searches through his money stash to make change. Even a skilled driver needs a half a minute to conduct such a transaction, so if you have three or four passengers who need to make change, said Mezuman, that’s an extra two minutes spent waiting with the motor running.

Even an “exact change” transaction by an efficient passenger takes 10-20 seconds, as the passenger drops the fare into the slot and waits to get a receipt. “And then you have the ‘grand prize’ scenario, where the driver runs out of change and the passenger has to ask other people if they can break a bill,” said Mezuman. “In that scenario, all bets are off.”

While a two or three minute delay doesn’t sound too bad, Mezuman said, you have to multiply that by the number of stops the bus makes on its route. “In the end we are talking about 20 minutes or more wasted on making change,” said Mezuman. “HopOn eliminates or cuts down on that wasted time significantly.”

The ultrasonic tones used by HopOn are unique to the app, said Mezuman. “We developed this technology over several years to ensure that no mistakes would be made, that the sounds we use cannot be mistaken for something else and used by another app, or compromised by a passenger who tries to get on the bus for free.”

Once a passenger boards a bus, the app registers that they have paid the fare, and an electronic receipt appears on the user’s device, suitable for presentation to fare inspectors who check to see if the right fare was paid.

“If passengers are boarding a bus that has multiple fares, such as an inter-city bus where they pay according to distance, the app will ask what stop the passenger is getting off at, and charge the credit card appropriately, “said Mezuman. In that sense, the app works the same as a cash payment. “Passengers who tell the driver that they are getting off sooner than they really planned to in order to pay a lower fare and are caught by an inspector have to pay a fine, and that would apply if the passenger used HopOn to pay and shortchanged the bus company.”

The are some benefits for the bus companies as well. “They save money on the paper they don’t have to use to print receipts, and on the gas they don’t burn off because the trip is a half hour faster,” said Mezuman. In addition, companies outfitting new buses won’t have to buy a validator, a device that registers the passenger’s payment. “With HopOn, the phone is the validator, so companies save money on that, too.”

The company has raised several hundred thousand dollars from angel investors and is in pilot programs with six Israeli bus companies. “Within a few months we expect to be certified for use on all Dan company buses in the Tel Aviv area,” said Mezuman. “We have been working to implement this with the bus companies in Israel for the past year and a half. The bus business is slow-moving, and there is a lot of regulation involved, so it’s a gradual process.”

Mezuman has also been speaking to bus and train companies abroad and expects to install the system in a transportation company in Monaco soon. “We’ve put a lot of work into this, and we believe it will pay off for passengers and companies,” Mezuman said. “Everyone who has tried HopOn loves it.”

Especially the passenger in line behind the guy waving the 200-shekel bill.