Every application here says what it does, which SAE J2735 messages and standards it runs on, who cares about it and where it stands: 27 of them run in our training simulator with real message bytes, the rest are deployed, piloted, specified on paper or still being argued about. Pick your audience and a status to shorten the list. New to the subject? Read what the community is wrestling with in 2026 first.
The OBU matches its lane to the MAP, reads the SPaT countdown for its signal group and warns when the vehicle cannot clear the stop bar before red.
What holds it back. Needs a surveyed MAP that is kept current and a controller that streams SPaT with honest min and max end times; both are agency work that outlives the pilot.
SAE J2735 SPaT and MAP, CTI 4501 Connected Intersection, SAE J2945/10 (MAP and SPaT content)
On a red with a known time to green, the OBU computes the speed that reaches the stop bar as the green starts and shows it to the driver (or hands it to adaptive cruise). Fewer stops, less fuel, smoother platoons downstream.
What holds it back. Only works where SPaT countdowns are reliable, which rules out fully actuated signals without good prediction; drivers also ignore a speed advisory unless the car does it for them.
SAE J2735 SPaT and MAP; USDOT AERIS program (GlidePath prototype at Turner-Fairbank)
While a vehicle waits to turn left on a permissive green, the OBU watches the BSMs of oncoming through traffic and warns when the gap is too short.
What holds it back. Needs the oncoming vehicle to be equipped, so it pays off only once a good share of the fleet carries an OBU.
SAE J2735 BSM, SAE J2945/1; one of the V2V safety applications in NHTSA's 2014 V2V readiness report
A radar or camera on the pole tracks every road user in the box; an edge device turns the tracks into SDSMs so equipped vehicles hear about pedestrians, cyclists and cars that carry nothing. The same message lets a vehicle share what its own sensors see.
What holds it back. Sensor accuracy, object matching and who is liable for a wrong detection are open questions; few OBUs consume SDSM yet. Turn it on in the simulator's RSU step.
SAE J3224 Sensor Data Sharing Message, PSID 0x8010
Turning drivers are warned when the pedestrian phase is WALK or a PSM shows someone in the crosswalk on their path. Piloted in the New York City and Tampa connected vehicle pilots.
What holds it back. Few pedestrians carry a device that sends PSMs; the SPaT-only version warns about a phase, not a person, so it over-warns.
SAE J2735 SPaT pedestrian signal groups and PSM, SAE J2945/9 (VRU)
The intersection tells a driver on the minor street when the gap in the main street traffic is too short, or warns the cross street that a vehicle is about to run the red.
What holds it back. Depends on either full fleet equipment or roadside sensors with SDSM; the stop sign version was prototyped and never deployed.
SAE J2735; application concepts from the USDOT V2I safety program
The bus sends a Signal Request Message with its lane and arrival time; the controller answers with a Signal Status Message and extends the green or brings it early. Utah DOT runs it statewide on buses and snow plows; other agencies followed.
What holds it back. Controller firmware and the priority logic differ by vendor, and the agency has to decide how much side-street time it will give up.
SAE J2735 SRM and SSM, NTCIP 1211 signal control and prioritization, NTCIP 1202
An emergency unit on a run asks for preemption; the controller clears to its phase and holds it. Its BSM says lights and siren are on so other equipped drivers get an alert before they hear it.
What holds it back. Agencies already own optical or GPS preemption and want proof that V2X is cheaper or safer before they swap; mixed fleets run both for years.
SAE J2735 SRM (role emergency, fire, police) and BSM SpecialVehicleExtensions
Heavy trucks get a green extension so they do not stop and restart at every signal on a port or industrial corridor. Piloted on freight corridors in several states.
What holds it back. Truck fleets are not agency fleets, so somebody has to equip them and the agency has to trust the request.
SAE J2735 SRM role truck, importance level set by the agency
Plows and maintenance trucks keep moving through signals during a storm. Runs in Utah on the state plow fleet.
What holds it back. Needs the fleet equipped and a policy for when the priority applies.
SAE J2735 SRM role dot or roadWork
Equipped drivers are told an emergency vehicle is approaching, from which direction, before they can hear it. Part of the Tampa and Wyoming pilots.
What holds it back. Only as good as the share of emergency fleets with OBUs; most agencies equip them first, so this one is ahead of the others.
SAE J2735 BSM SpecialVehicleExtensions (sirenUse, lightsUse)
A portable RSU broadcasts the closure, the advisory speed and the region; equipped drivers slow and merge before the arrow board. Piloted in Wyoming, Tampa, Colorado and others; our map builds the TIM from live WZDx feeds.
What holds it back. Keeping the message truthful as the work zone moves is a workflow problem; agencies that already publish WZDx are closest.
SAE J2735 TIM with ITIS codes, SAE J2945/4 Road Safety Message (lane-level work zones), WZDx feeds
The RSU learns where the queue tail is from BSMs or detectors and broadcasts a stopped-traffic TIM so drivers brake before they can see the queue, which is where work zone rear-end crashes happen. The Tampa pilot ran an end-of-ramp version.
What holds it back. Detecting the tail reliably without many equipped vehicles means detectors or sensors; the TIM has to be refreshed every few seconds.
SAE J2735 TIM (ITIS 257 stopped traffic); USDOT INFLO prototype (Seattle I-5, 2015)
Variable advisory speeds pushed to equipped vehicles upstream of a bottleneck to flatten the shock wave. Our corridor's reduced-speed frame is the static version.
What holds it back. Prototyped, not deployed through V2X; variable speed limit signs do the same job for everyone today.
SAE J2735 TIM advisory speed; USDOT INFLO prototype
A TIM over the approach to a sharp curve with the advisory speed; the display escalates as the driver nears it. Among the first infrastructure applications in the USDOT safety pilots.
What holds it back. A static curve sign does most of this; the V2X version earns its keep when it changes with weather or vehicle class.
SAE J2735 TIM advisory with a region on the curve
Ice, fog or high wind on a stretch of road as a TIM with an advisory speed. The Wyoming pilot built its whole program around weather alerts on I-80.
What holds it back. Needs a trustworthy weather source, often the agency's own RWIS and plow reports; stale alerts kill credibility.
SAE J2735 TIM (ITIS ice, slippery), SAE J2945/3 road weather applications
A TIM with the clearance ahead; an OBU that knows its vehicle height warns only the trucks that do not fit.
What holds it back. Few OBUs carry the vehicle's height today; bridge strikes keep this one on agency lists.
SAE J2735 TIM (ITIS height limit)
Ramp detectors see the wrong-way entry and the RSU broadcasts a TIM to the oncoming traffic; equipped vehicles also see a BSM heading against the lane. Texas and Florida agencies run the detection side at scale.
What holds it back. The detection is deployed, the V2X alert is not: there are not enough receivers yet.
SAE J2735 TIM; wrong-way detection by radar or thermal cameras at ramps
A stalled vehicle or a crash scene becomes a TIM for the approach; responders' vehicles can also flag themselves in their BSMs. Incident scene work zone alerts were a Tampa and USDOT responder safety theme.
What holds it back. Somebody has to create the message quickly; agencies tie it to the TMC incident workflow or it never gets sent.
SAE J2735 TIM (ITIS stalled vehicle), BSM VehicleEventFlags
A regulatory frame with the limit and the hours it applies, so the car's speed advisory changes with the flashing beacon.
What holds it back. Simple to broadcast, rarely done because the vehicle side is not there yet.
SAE J2735 TIM roadSignage frames with a speed limit
Open spaces at the next rest areas pushed to trucks as a TIM so drivers stop looking for parking at the end of their hours. The data exists (our map shows it); the in-cab delivery over V2X does not.
What holds it back. Truck OBUs are rare and the fleets get the data through telematics today.
TPIMS feeds (MAASTO states) carried as TIMs; see the live truck parking layer on our map
An RSU at a grade crossing warns a driver who will not stop in time when the gates are coming down, from the crossing's own signal state.
What holds it back. Prototype only; railroads and highway agencies own different halves of the crossing.
SAE J2735; USDOT RCVW prototype built on V2X Hub
Closing fast on an equipped vehicle ahead, the OBU computes the time to collision from its BSMs and warns.
What holds it back. Radar FCW is standard on new cars, so the V2X version is a complement for hidden vehicles, not a seller.
SAE J2735 BSM, SAE J2945/1 (10 Hz BSM, path history and prediction)
A hard brake several vehicles ahead reaches the whole queue in a tenth of a second, through the vehicles that block the view.
What holds it back. Needs equipped vehicles in the same queue; the first real benefit comes with fleets that travel together.
SAE J2735 BSM VehicleEventFlags eventHardBraking
On a two-lane road, the oncoming vehicle's BSM says whether a pass would meet it in the curve.
What holds it back. Rural two-lane roads are where this helps and where equipped vehicles are scarcest.
SAE J2735 BSM
At a stop-controlled or blind crossing, the OBU warns when a cross vehicle's BSM says it will arrive at the same time, before it is visible.
What holds it back. Depends on both vehicles being equipped; the roadside SDSM version is the way around that.
SAE J2735 BSM; a core NHTSA V2V safety application
A vehicle in the blind spot or closing fast in the target lane, known from its BSM rather than a radar.
What holds it back. Radar blind spot monitors shipped first; the V2X version adds range and works around trucks.
SAE J2735 BSM
An equipped vehicle whose BSM heading opposes the lane is flagged to everyone in range, no roadside detector needed.
What holds it back. The wrong-way driver is rarely the equipped one.
SAE J2735 BSM heading against the lane direction
A right-turning driver is told about the cyclist going straight in the curb lane (the right hook), from the bicycle's PSM or from the roadside sensor's SDSM.
What holds it back. Bicycles rarely carry a transmitter; the sensor route is what agencies are looking at.
SAE J2735 PSM (aPEDALCYCLIST), SAE J3224 SDSM, SAE J2945/9
The bus driver is warned of pedestrians in the crosswalk the bus is turning into, and pedestrians at the stop are warned of the bus pulling in.
What holds it back. Needs PSMs from phones or a roadside sensor; transit agencies want it for the turn conflicts their drivers cannot see.
SAE J2735 PSM; Tampa pilot bus application
A phone places the pedestrian call and reads the WALK state back to a visually impaired person, with the crossing geometry from the MAP.
What holds it back. Piloted in New York; needs accessible-device integration and an agency willing to accept calls from phones.
SAE J2735 (New York City pilot PED-SIG application for visually impaired pedestrians)
The following vehicle reads the leader's speed and acceleration from its 10 Hz BSMs and holds a 0.6 s gap where a driver needs 1.2 s or more. FHWA and several truck makers ran platooning trials; Utah tested it on plows.
What holds it back. State rules on following distance, driver acceptance and the business case for two-truck platoons slowed it; the technology works.
SAE J2945/6 (CACC and platooning), SAE J2735 BSM
Vehicles negotiate a merge or a lane change by sharing intended maneuvers, and the infrastructure can referee at a ramp or a work zone taper. The USDOT CARMA platform and CARMA Streets are the reference implementations.
What holds it back. No production vehicle sends maneuver messages yet; the J3186 message set is young and the liability questions are open.
SAE J3186 Maneuver Sharing and Coordinating Message, SAE J3216 CDA taxonomy, USDOT CARMA
An automated driving system treats SPaT as a second source of truth beside its cameras and uses the MAP for lane topology; an SDSM fills its blind spots at a corner. Deployment sites in Arizona, Texas and Utah under the USDOT V2X accelerator program include this theme.
What holds it back. AV developers want the data to be certified and signed before they trust it, which brings it back to MAP quality and SCMS.
SAE J2735, SAE J3224, SAE J2945/A (ADS)
A stuck automated shuttle gets help from a remote operator over the cellular network. Often listed beside V2X; it does not use the 5.9 GHz band at all.
What holds it back. Latency, coverage and who is driving under the law.
3GPP Uu (network V2X); no J2735 message
The gantry advertises the fees per vehicle class and the toll zone lanes; an equipped vehicle answers with a usage message and gets an acknowledgement at full speed, with the RSU on the gantry. No windshield transponder.
What holds it back. Toll operators have billions of transponders and plate cameras that work; the 2024 messages are new and no operator has committed.
SAE J2735 (2024) TollAdvertisementMessage, TollUsageMessage and TollUsageAckMessage; toll PSIDs assigned to the operator under IEEE 1609.12
Per-mile charging configured and reported through V2X messages instead of a plug-in dongle or odometer reading.
What holds it back. State RUC programs are still political; the messages were published in 2024 and nobody has used them on a road.
SAE J2735 (2024) RoadUserChargingConfigMessage and RoadUserChargingReportMessage (messageIds 48 and 49)
The advertised fee follows demand and reaches the vehicle before the decision point, so the driver (or the navigation) can choose the lane. Our toll scenario prices by the two-minute count at the gantry.
What holds it back. The price has to be the same one the signs show, which ties the TAM to the operator's pricing engine.
SAE J2735 TAM fee tables; agency pricing algorithms
RSUs log the BSMs they hear; the TMC gets speeds, travel times, hard braking hot spots and signal performance measures without loops. Our live page records BSMs from your own RSU and plots breadcrumbs.
What holds it back. Privacy rules on storing BSMs, and the small share of equipped vehicles, limit what the data says today.
SAE J2735 BSM and ProbeVehicleData, SAE J2945/12 (traffic probe)
Message stores, forwarding, radio settings and health of every RSU from the TMC through one standard interface. Our RSU registry pushes messages this way.
What holds it back. Vendors implement different subsets; the agency should test the MIB objects it needs before buying.
NTCIP 1218 v01A (January 2025) RSU management over SNMPv3
Every RSU and OBU signs its messages with certificates from a security credential management system; receivers drop unsigned messages and report misbehavior. Not an application, but every application depends on it.
What holds it back. Enrollment, certificate top-ups over the backhaul and who pays the per-device fee are the questions agencies ask first.
IEEE 1609.2 and 1609.2.1, the SCMS Manager's policies and the USDOT SCMS proof of concept
