This message is used to send alerts for nearby hazards to travelers. Unlike many other messages which use the LRMS profiles to describe the areas affected, this message likely applies to the receiver by the very fact that it is received. In other words, it does not use LRMS. Typically transmitted via V2X, this message provides simple alerts to travelers (both in vehicle and portable devices). Typical example messages would be “bridge icing ahead” or “train coming” or “ambulances operating in the area.” The full range of ITIS phrases are supported here, but those dealing with mobile hazards, construction zones, and roadside events are expected to be most frequently used. This message is for alerting about roadway hazards, not for vehicle cooperative communications, mayday, or other safety applications. It is generally presumed that each receiving device is aware of its own position and heading; but it is neither a requirement to receive and understand these messages, nor is having a local base map. The position section of the message gives a simple vector for where the hazard is located (fixed or moving) and can be used to filter some messages as being not applicable. Consider a “train approaching” message which indicates the train is in fact traveling away from the receiver. The basic information types themselves are represented in the standard ITIS codes sent only in their integer representation formats. This ITIS list is national in scope, never outdated (items can only be added), and in this use does not allow local additions. Refer to SAE J2540-2 for the complete code list. A priority level for the message is also sent, which may be matched to various other priorities in the cockpit to determine the order and type of message presentation to minimize driver distraction. Message transmission priority is typically handled in the IEEE 1609 standard layer in the application stack and is a function of the application type. A duration field provides a gross level for the range (distance) of applicability for the message over distance. For example, some messages are no longer meaningful to the traveler once the vehicle has moved a distance down the roadway link. In many cases, a complex event is explained in the other supporting ATISmessages, and a linkage value is given when it is available.

The signal request message (SRM) is a message sent by a V2X-equipped entity (such as a vehicle) to the RSU in a signalized intersection. It is used for either a priority signal request or a preemption signal request depending on the way each request is set. Each request defines a path through the intersection which is desired in terms of lanes and approaches to be used. Each request can also contain the time of arrival and the expected duration of the service. Multiple requests to multiple intersections are supported. The requestor identifies itself in various ways (using methods supported by the RequestorDescription data frame), and its current speed, heading, and location can be placed in this structure as well. The specific request for service is typically based on previously decoding and examining the list of lanes and approaches for that intersection (sent in MAP messages). The outcome of all of the pending requests to a signal can be found in the signal status message (SSM) and may be reflected in the SPAT message contents if successful.