In the first of a three-part series on Traveler Information Messages (TIMs), we explored TIMs essential role in enhancing road safety and operational efficiency. We also discussed how TIMs communicate with drivers and common challenges faced by transportation
agencies. In the second part, we dove deeper into the in-vehicle delivery of TIMs and their potential to improve driving
conditions. In our final installment, we will delve into TIM standards, which are crucial for ensuring nationwide interoperability and creating effective messages.
What Are Traveler Information Messages (TIMs)?
TIMs are geofenced Connected Vehicle messages based on the SAE J2735 standard. TIMs enhance safe and efficient travel on roadways by providing real-time updates to drivers regarding various road conditions, including:
- Traffic Conditions: Information on congestion, incidents, or road closures.
- Weather Alerts: Notifications about adverse weather conditions, such as snow, rain, or fog, that may affect driving or even cause road closures.
- Construction Updates: Alerts about ongoing road work that may affect travel routes, such as changes to speed limits or available lanes.
- Travel Times: Estimated travel durations for specific routes to help drivers plan accordingly.
- Emergency Alerts: Notifications about natural disasters, severe weather warnings, or other emergencies that could impact road safety.
Why are Traveler Information Messages (TIMs) Important?
TIMs play an important role in enhancing road safety for drivers. TIMs alert drivers to potential hazards like severe weather, encouraging cautious driving and reducing accident risk. In the event of a primary crash, TIMs can notify approaching vehicles,
helping to prevent secondary collisions and protecting both drivers and emergency responders.
In addition to improving safety, TIMs serve as an effective traffic management tool. Transportation agencies can use TIMs to reroute traffic during road closures or construction, which helps maintain smooth traffic flow and ensures public safety.
How are Traveler Information Messages (TIMs) Communicated to Drivers?
For over two decades, federal and state transportation agencies have prioritized providing real-time traveler information. One significant initiative is the 511 system, which is now widely available in almost all states, offering essential information
about road conditions. However, despite being widely available and accessible on personal mobile devices, many drivers do not utilize the service.
Dynamic Message Signs (DMS) are another way to deliver real-time TIMs. With the integration of connected vehicle (CV) technology, new opportunities have emerged for enhancing TIM delivery. In-vehicle systems, utilizing C-V2X (cellular vehicle-to-everything
communication), satellite, or cellular networks, offer the potential to deliver TIMs directly to drivers.
While the use of connected vehicles for TIM communication is still in development, some states have already implemented systems capable of accommodating these advancements, significantly enhancing the delivery of TIMs.
Part 2
Imagine driving on a seemingly safe, well-maintained road in a remote winter area. Despite clear skies and adherence to speed limits, you unexpectedly encounter a hidden patch of black ice, causing you to lose control of your vehicle. Similarly, you might
not notice a stalled vehicle ahead while driving through fog until it's too late to slow down and avoid a collision. These situations are not limited to weather conditions; they can also involve unexpected traffic queues or lane closures due to various
events.
In these cases, the key to avoiding an accident is having advance warning. Drivers need to be aware of hazards before so that they can react appropriately—whether by reducing speed or taking evasive action. While Dynamic Message Signs (DMS)
can provide some of this information, they have limited availability and are not capable of delivering geofenced or customized messages. This is where in-vehicle TIMs prove invaluable, delivering customized information tailored to the vehicle's
precise location and direction.
How to Provide In-Vehicle TIMs
While being able to alert drivers in a vehicle can be extremely valuable, it comes with some risks if the information is not accurate. Since drivers in vehicles are slow to trust and quick to dismiss messages if they are deemed inaccurate, it
is essential that DOTs only push reliable TIMs. For in-vehicle TIMs to be accurate, reliable, and timely, several critical components must be in place, including dependable input data and an efficient message creation and delivery system.
Input Data for TIMs
The reliability of TIMs depends on the accuracy and trustworthiness of the input data. Most TIMs are generated using data from agencies’ Advanced Transportation Management Systems (ATMS), where information has already been vetted and confirmed
as reliable. While some processes can be automated, many still involve human oversight to ensure data accuracy.
In addition to ATMS data, other potential sources include third-party data, crowdsourced information, Connected Vehicle (CV) data from Basic Safety Messages (BSMs), or data from Original Equipment Manufacturers (OEMs). While many of these data
sources can be reliable, cross-verifying information from multiple independent sources is recommended. Even with multiple data inputs, agencies should review and approve the information before generating TIMs and delivering them to drivers.
TIM Creation Process
The process of creating TIMs can be either manual or automated. Manual TIM creation involves direct input from Traffic Management Center staff, which can be time-consuming and add to their workload, potentially leading to errors or delays in message
distribution.
Automated systems can efficiently analyze available data, generate TIMs, and distribute them to the CV network or third parties for in-vehicle delivery. For instance, CORVUS is a tool capable of automating TIM creation and distribution. Regardless of whether message creation is manual or automated, adhering to established
standards is crucial to ensure nationwide TIM interoperability.
In-Vehicle TIM Delivery
Several technologies can be used to deliver TIMs directly to vehicles. Connected Vehicle (CV) technology requires significant infrastructure, including Roadside Units (RSUs) and Onboard Units (OBUs) installed in vehicles. CV technology enables
not only TIMs but also other important safety messages. As agencies continue to invest in CV infrastructure, this method of communication is expected to become more widespread in the coming years.
Other delivery methods include third-party services such as navigation apps, radios, or infotainment systems, which are already in place and can communicate TIMs via satellite or cellular networks. Third-party technologies are especially useful
in remote or rural areas, where cellular or satellite communications can transmit essential messages like TIMs more easily. To facilitate this, agencies must establish a data exchange platform to manage communication with third parties. One
such platform is the Situation Data Exchange (SDX), which allows agencies to send TIMs to third parties
for in-vehicle broadcasts.
Part 3
The most recognizable form of TIMs is those displayed on Dynamic Message Signs (DMSs). DMSs primarily display traffic operations, regulatory information, warnings, and guidance. In some cases, they may also provide safety messages, transportation-related
notifications, and emergency alerts, such as AMBER and Blue alerts. While states can issue guidelines for DMS message content and format, their architecture, message content, and graphics are standardized under NTCIP 1203 v03.05.
Beyond DMSs, the Manual on Uniform Traffic Control Devices (MUTCD) governs physical road signage and markings. However, a distinct set of standards applies to in-vehicle TIM delivery.
TIM Standards for In-Vehicle Delivery
In-vehicle TIMs often provide the same or similar information as physical signs and DMSs but operate under distinct standards. TIMs can deliver both regulatory and warning messages, offering various alerts to drivers. The primary standards
for TIMs include:
SAE J2735: This standard outlines how information is represented when transferred between systems. It defines the data structure, including dialogues, messages, data frames, and elements.
SAE J2540-2: Known as the International Traveler Information Systems or ITIS Phrase List, this standard specifies message content and phrasing. While it does not define the graphical display of TIMs within vehicles, it does recommend MUTCD signs for certain phrases to maintain consistency and ensure ease of understanding for drivers.
However, where phrases are not linked to MUTCD signs, deployers or broadcasters may have their own guidelines for how TIMs should be displayed in-vehicle.
Ensuring TIM Interoperability
As Connected Vehicle (CV) technology evolves, the interpretation of standards and deployment practices introduces challenges related to interoperability. The flexibility in TIM definitions also poses potential issues, as several key message
elements are optional but can significantly impact communication, especially as the volume of TIMs increases and real-time information changes. Ensuring interoperability requires a more explicit coordination of these elements, including:
TIM Unique ID: This allows a receiver to source TIMs from different providers, such as Roadside Units (RSUs) and third-party services.
TIM Message Count: Facilitates message updates by indicating revisions.
TIM Data Frames: Supports multiple messages within a single data frame.
TIM Timing and Duration: Defines the start and end times of a message, with flexibility on end time as an option.
In addition to message consistency, interoperability at the security level is also essential. This can be achieved through the Security Credential Management System (SCMS), which defines where and how TIMs are digitally signed to ensure secure
communication between vehicles and infrastructure.
Addressing Standards and Best Practices
Several ongoing deployments are working to establish a best practice guide to standardize TIM creation and ensure that messages are clear and usable by both human drivers and autonomous vehicles. The goal is to achieve uniformity in TIMs across
various regions, road types, and traffic conditions, ensuring that all road users, regardless of location, receive accurate and timely information.
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