Definition
ITS (Intelligent Transport System) is the intelligent transportation system, which uses traffic signals, RSU, magnetic vehicle detectors, VMS guiding screens and other roadside devices to achieve signal networking, V2X vehicle-road coordination, and traffic monitoring.
System Composition
ITS covers subsystems such as signal control, traffic monitoring, information dissemination, and vehicle-road coordination. Traffic signals control the intersection lights, supporting networked coordination and green wave optimization; magnetic, video, radar, and other vehicle detectors collect flow and occupancy data; RSUs deploy C-V2X for communication with on-board OBUs; VMS guiding screens provide information such as traffic conditions and speed limits. All devices are connected to the central platform via wired or wireless networks for unified scheduling and data analysis.
Applications of communication modules
Roadside devices are widely distributed, wired network deployment is costly, and 4G/5G modules have become important networking means. RSUs, traffic signals, vehicle detectors, guidance screens, etc., communicate with cloud platforms or regional centers through modules to report traffic data and receive control instructions. 5G's low-latency characteristics support V2X vehicle-road coordination, enabling RSUs to deliver traffic conditions and signal light statuses to vehicles, assisting in autonomous driving and safety warnings. Modules need to support industrial-grade specifications, wide temperature ranges, and high reliability to adapt to harsh outdoor environments.
Coordination with V2X
ITS and V2X deeply integrate: RSUs act as roadside nodes, aggregating data from traffic signals, vehicle detectors, etc., and broadcasting it to vehicles via C-V2X; vehicles report their own status to RSUs, and the platform consolidates this data to form a global traffic overview. Communication modules in RSUs and OBUs perform cellular backhaul and C-V2X communication, serving as key components of intelligent transportation and vehicle-road coordination.
Engineering Practice Supplement
Cross-team coordination for "ITS": hardware provides impedance and power budgets, RF provides spurious and sensitivity margins, embedded systems define thread models and storage lifespans, and the cloud defines SLA and rate limiting. For NB-IoT scenarios, the business model must match wake-up cycles, packet lengths, and downlink capacity; for onboard and mobile scenarios, session retention during handover and roaming must be considered. At project closure, conduct a "red team" style review: whether behaviors are defined for weak networks, power outages, certificate expiration, clock jumps, and full storage.
Roadside samples and timing commands
An intelligent transportation system closes a loop of detection, control, and display on junctions and road sections. Magnetometers, video, or radar supply flow and occupancy. The signal controller changes lamp colors from a timing plan. Variable message signs publish speed limits and guidance. A roadside unit then sends lamp state and alarms to vehicles. The communication module here is the backhaul. It does not replace the lamp interlock inside the controller. The safety logic of a lamp change belongs on the local controller. The cellular link uploads detections and downloads a new timing plan or a time sync. A downloaded plan needs a version and an effective time. Until the junction has received and checked it, the junction keeps running the current plan.
Cellular backhaul fits when power and grounding at the pole are already solved, the local controller has a degraded timing plan it can run if the link breaks, and the clocks can be aligned to one time base. An air interface that needs millisecond vehicle-to-vehicle coordination does not travel as ordinary internet access on the public cellular network. Direct roadside-to-vehicle radio is a separate system. During construction, if detectors are not yet calibrated, unchecked flow should not be used to change the cycle automatically.
Backhaul delay that scrambles a green wave
Detect, compute the lamp color in the cloud, then send the color back. If the delay and jitter on that path are longer than one phase, coordinated control is worse than a local fixed plan. When the module attaches over and over, detection messages pile up and are replayed in one burst. If the platform aligns them by arrival time rather than sample time, it treats old congestion as current congestion. If the controller and the platform disagree on time zone or daylight saving, the absolute time of the green wave shifts as a whole. When the SIM runs out of credit or a billboard blocks the antenna, the site still shows the last plan that was sent, while the operations screen marks the site online. A metal pole changes the antenna pattern, and the lab rate does not reappear on the pole.
Every detection and every command should carry sample time, junction ID, and plan version. Discard an expired command. Whether a delay-sensitive service can actually be bought is a question for QoS and service flows, not an assumption that a 5G bearer means low latency. After power returns, run the local safe plan first, accept central control only after time sync succeeds, and do not move a phase into a conflicting direction on a wrong time base.
Commands and detections both carry sample time, junction ID, and plan version. The platform orders them by sample time and does not rewrite a phase by arrival time. Discard an expired plan. Do not execute it late. After the link has been down longer than the agreed time, the junction keeps its local degraded timing. After the link returns, sync time before accepting central control. When the module is mounted on a metal pole, retest the antenna direction. The lab rate is not the rate on the pole. Until detectors are calibrated, use the data only for monitoring, not to change the cycle automatically. If clock sources disagree, stop coordinated control first, so the absolute time of the green wave does not shift by a whole phase.
Leave lamp interlocks on the junction controller. The backhaul carries detections and a new plan that has been checked. Before the effective time of a plan is interpreted on the local clock, finish time sync. If a replayed detection is later than one timing cycle, archive it and do not let it join the current control. Tell an offline site caused by a blocked antenna or an unpaid SIM apart from a detector that sees no vehicles, so a communication fault is not counted as an empty road.