Passengers switching trains in Amsterdam and Rotterdam are often caught paying twice with their contactless smart cards, according to squidcard.com.
According to Dutch News, the double charge occurs when customers cross networks run by different transport companies. Because each company uses its own system, no set fee has been established.
The smart card system, called ov-chipkaart, was established earlier this year and is the only form of payment accepted on the metro in the two cities.
According to squidcard, Londoners have had no such trouble using their Oyster smart cards when paying for the metro, since the different companies all support the same system.
Additionally, London mayor Boris Johnson announced this week that Londoners will be able to use their Oyster cards to pay for above-ground train services as well as the metro.
Read more here.