In 2020, Utah became the second US state to implement an optional road user charging (RUC) scheme for certain light vehicles. Optional in the sense that such vehicles could choose either to pay a higher annual vehicle registration fee or pay RUC instead. 

Utah's scheme is only available to electric vehicles, plug-in hybrids and conventional (petrol powered) hybrid light vehicles.  They each face a choice as follows:

Electric:    (US) $120 a year registration fee or US$0.015 per mile (up to a cap of $120)

Plug-in Hybrid: $52 a year registration fee or $0.015 per mile (up to a cap of $52)

Conventional Hybrid: $20 a year registration fee or $0.015 per mile (up to a cap of $20)

The reason for the lower fees for plug-in hybrid and conventional hybrid vehicles is to acknowledge that they all pay state fuel taxes in addition to these fees, although of course, this means that conventionally hybrids that are driven more than 1334 miles per annum, pay nothing more than fuel taxes at that point.  

The main technology option available to motorists has been to acquire an On Board Diagnostics (OBD-II) plug-in device that is inserted into the OBD-II port on the vehicle, which receives data generated by the vehicle's on-board systems, includes a GPS receiver and transmits the trip data via the mobile telecommunications network. In addition, the vehicle owner must download an app and take a single image of the vehicle's odometer at the point of registration, and then an annual odometer image is taken and transmitted to verify distance travelled.

However this has is supplemented by another option, which in its own way, is quietly revolutionary in the world of RUC. Whether it is called embedded telematics or Original Equipment Manufacturer (OEM) telematics, it is the telematics system built into a vehicle at the time of production.

What this means is that for vehicles able to use this option, no additional equipment is required, with the vehicle already equipped to record trip data by distance, location and time of day.  Tesla Model 3 cars do not have OBD-II ports, so a smartphone is used to connect with the vehicle's telematics system to access the trip data and transmit it to the service provider.  An API is provided to enable access of that data by the smartphone using the relevant app (Smartcar).  Of course this relies on the driver bringing the phone with the relevant app, pairing it with the vehicle and ensuring the phone remains powered throughout the trip.  It's not clear whether forgetting to carry the phone becomes a problem, because next time the phone is connected to the vehicle it could access such data once more. 

The system is intended to be expanded to other Tesla models, but would be greatly improved if the telematics system connected directly to the service provider rather than simply paired with a phone. There are likely to be some key enforcement challenges if it becomes phone dependent, because the incentives to connect your phone to the car for the purposes of paying RUC are not good.  

However, this IS a significant step forward. Most vehicles nowadays are built with embedded telematics, but until Utah, none have been used for RUC. There are considerable barriers to making it work, not least consent from the vehicle manufacturer, and the diversity of such systems on-board vehicles (some will not be sufficiently reliable, some won't be sufficiently secure). However, if these issues can be addressed, RUC would simply be another application for such systems to record and report trip data.

Without the need for any additional equipment, the capital costs of RUC drop considerably, and the operating costs are mostly around managing customer service and communications.  Have no doubt, there is a long way to go to enable this, and there are considerable barriers, but Utah has pioneered RUC using technology built into cars.