Updated 2026-10-14
Why this page exists
Agencies ask us the same dozen questions, and the trade press, ITS America, ITE and the USDOT ITS Joint Program Office keep circling the same themes. This page states each one plainly, says what is settled and what is not, and points to the part of this site where you can try the piece that matters. Dates and rule citations below are the ones we could verify in the Code of Federal Regulations and the FCC's order; the rest is the state of the conversation as we hear it, and we say so where a number is soft. The applications catalog lists what each application needs and where it stands.
1. The DSRC cutoff is December 14, 2026
The FCC's Second Report and Order in docket 19-138 (FCC 24-123, adopted November 20, 2024) ended the long spectrum fight. DSRC licenses in the 5.9 GHz band terminate two years after the rules were published in the Federal Register, and 47 CFR 90.7 now carries the date: December 14, 2026. New licenses issued since the rules took effect authorize C-V2X only, and the earlier C-V2X waivers ended when the final rules took effect. Agencies with DSRC roadside units still running have weeks, not years, to replace or re-flash them, and many of the early pilot sites (Tampa, New York, Wyoming, Ann Arbor, Georgia) have been doing exactly that. The portal does not support DSRC-era RSU specifications for this reason; everything here targets C-V2X, NTCIP 1218 v01A and the 2024 message set.
2. The new channel plan and power rules
The upper 30 MHz (5.895 to 5.925 GHz) is split into three 10 MHz channels (5.895 to 5.905, 5.905 to 5.915 and 5.915 to 5.925 GHz) that a licensee may combine into 20 MHz or a single 30 MHz channel. Roadside units run under Part 90 subpart M at up to 33 dBm EIRP with the antenna's radiation center no more than 8 m above the roadway at full power, reduced by 20 log(h/8) dB up to 15 m, and nothing above 15 m. On-board units are licensed by rule under Part 95 subpart L, at 23 dBm EIRP in the lowest 10 MHz channel and 33 dBm (27 dBm within 5 degrees of horizontal) in the upper channels unless the unit is geofenced outside the federal radiolocation coordination zones. Every RSU must be registered in the FCC's Universal Licensing System before it transmits. The simulator's RSU step enforces the 33 dBm ceiling and the FCC licensing guide walks through the registration.
3. Which 3GPP release, and will they talk to each other
The FCC deliberately did not pick a 3GPP release. LTE-V2X (Release 14) is what the deployed radios and the SAE J3161/1 profile use; NR-V2X (Release 16 and later) is not interoperable with it on the same channel. The practical answer in 2026 is Release 14 for anything that has to work with other people's equipment, and a procurement clause that asks the vendor how they will handle a later migration. OmniAir plugfests are where that interoperability gets tested; our certification guide says what to ask for.
4. Who runs the security credential management system, and who pays
Every production RSU and OBU signs its messages under IEEE 1609.2 with certificates from an SCMS. The USDOT proof of concept is over and commercial SCMS providers carry the load, with the SCMS Manager publishing the policies they follow. The open questions are the per-device cost of enrollment and certificate top-ups, how an agency with two hundred RSUs keeps them all enrolled across vendor changes, and misbehavior reporting: who decides a device is lying and revokes it. In the simulator, an unsigned RSU is ignored by the OBUs, which is the right behavior and the reason enrollment belongs in the first phase of a project, not the last. See the SCMS guide.
5. Not enough equipped vehicles
Infrastructure applications pay off in proportion to the vehicles that can hear them. Automakers have shipped C-V2X in a few models and announced more; the volume fleet is years out. The agencies that see results today equip their own fleets first: buses, plows, emergency vehicles, freight partners. Signal priority and preemption work on day one for those fleets. That is why the simulator's score panels always compare equipped against unequipped, and why aftermarket OBUs and the hardware build-out matter more than the OEM timeline for an agency deciding this year.
6. Cooperative perception and the roadside sensor
The Sensor Data Sharing Message (SAE J3224) lets an RSU with a radar or camera describe every road user it tracks, so an equipped vehicle learns about the pedestrian without a phone and the car without an OBU. It is the most-discussed answer to the fleet penetration problem and the least deployed: the sensor has to be accurate, objects must not be double-counted when a vehicle also sends its own BSM, and nobody has settled who answers for a wrong detection. Turn SDSM on in the simulator's RSU step and watch which warnings appear that could not have otherwise, and read the SDSM guide.
7. MAP accuracy and upkeep
The MAP is the one message that is never finished. Lane geometry has to match the paint within a lane width, and it changes with every restriping, turn lane and construction season. Agencies that treated the MAP as a one-time survey have found their red-light warnings firing in the wrong lane. The Connected Intersection standard (CTI 4501) and SAE J2945/10 give the content rules; our map builder draws MAPs from real carriageway geometry and the MAP guide covers the checks.
8. Signal timing data that tells the truth
A SPaT message is only as good as the controller's min and max end times. Fully actuated signals make poor predictions by construction; coordinated and fixed-time signals do well. Red-light warning and eco-approach both depend on this, and so does the ongoing argument about whether an agency should publish countdowns it is not sure of. The simulator's controller predicts its own countdown by running the ring-barrier logic ahead, and the signals dashboard shows what a priority call does to it. Start with how signal timing works.
9. Cellular V2N versus direct PC5
Traveler information, work zone data (WZDx), weather alerts and even SPaT reach phones and navigation apps over the mobile network today, with no roadside unit involved. The direct 5.9 GHz radio wins where latency and no-network operation matter: collision warnings, priority at the stop bar, platooning. The 2026 conversation is about which applications belong on which path and how an agency publishes once for both. Our CV2X map shows the public feeds that already exist and the J2735 message each would become.
10. Funding and the accelerator sites
Federal money has gone to a few sites as national models under the USDOT V2X deployment program (Arizona's Maricopa County, Texas A&M, Utah DOT), alongside SMART and other discretionary grants. Everyone else is budgeting RSUs into signal projects, fiber projects and work zone contracts one intersection at a time, which is where the equipment checklist in the simulator and the hardware build-out come in.
11. Cybersecurity, privacy and the vehicle bus
Agencies are asked two separate questions: is the roadside secure (no public IP on the RSU, VPN to the TMC, signed messages, patched firmware) and is the data private (BSMs carry temporary IDs that rotate, and stored probe data must be handled under state privacy law). On the vehicle side, an aftermarket OBU reads the CAN bus to fill the BSM and should never write to it on a public road; ISO/SAE 21434 and NHTSA's cybersecurity best practices are the references. The build-out page explains the CAN interface and where bench injection is legitimate.
12. Applications waiting for a reason to exist
Queue warning, speed harmonization, cooperative merge, platooning, tolling by OBU, road usage charging, rail crossing warnings and truck parking alerts all have messages and in many cases a pilot behind them, and none runs at scale. In most cases the reason is one of the items above: too few receivers, a business case that belongs to a different agency, or a standard that was published in 2024 and has not had time. The applications catalog marks each one by status and audience, and the simulator now runs queue warning, platooning, eco approach, left turn assist and tolling so you can judge them with your own numbers before you argue for them.
Where this leaves an agency in late 2026
Replace any DSRC unit before December 14; register every RSU in ULS; put SCMS enrollment and MAP maintenance in the first phase; equip your own fleet before counting on OEM vehicles; pick Release 14 C-V2X and ask about migration; and choose applications by who already has the equipment to use them. ITS Roads does this work for agencies; the contact page is the place to start, and the feedback form is where to tell us what this page should add.