Knowledge Resources

This project represented the continuing efforts of the Pennsylvania Turnpike Commission's to implement and integrate the use of ITS technologies throughout their roadway network. For this Advanced Traveler Information System (ATIS) deployment 12 variable message signs (VMS) were added for operational needs (as defined by the Commission), 8 closed circuit television (CCTV) cameras were added at interchanges with high Average Daily Traffic (ADT), 21 highway advisory radio (HAR) signs were used to fill in the gaps at the interchanges, 4 roadway information systems (RWIS) were deployed at areas with the worst weather conditions, 31 traffic flow detection systems (TFDS) were deployed at areas with high ADT, and 1 truck rollover warning system (TRWS) was deployed at an interchange that experienced high rollovers. These projects followed the typical Request for Proposal (RFP), Design, Bid, and Build process. Based on the Pennsylvania Turnpike Commission's experience, the following lessons learned are presented regarding the design of ATIS systems.

• Know and understand your needs. At the beginning of any project, a needs assessment should be conducted to ensure that the needs of different stakeholder groups are considered.
  • For this project, the Commission had many internal stakeholder groups, including operations, engineering, information technologies (IT), maintenance and management. Based on input from these groups, the Commission determined the operational, design, and integration needs for the project. In addition, surveys were conducted among users (Turnpike travelers) in order to assess the needs of the customer. Efforts were made to design a system that would meet the needs of both the internal stakeholder groups and the external groups (end users).
• Know your communication system limits. At the outset of the project, a telecommunications assessment is critical to understanding the limits of the system in which the ATIS will be deployed. It is important to identify all private (microwave backbone, Wide Area Network , or fiber) or public (Frame Relay Network, Asynchronous Transfer Mode, or Plain Old Telephone System) communication networks. Once the communications system has been evaluated, the amount of network expansion for future ITS projects or other agency projects need to be identified. For individual projects, the required bandwidth and time frame for the identified needs should be charted and tracked.
  • For this project there were two issues with understanding the communication system and its limits. First, miscommunications between internal Commission stakeholders led to an overestimate of available bandwidth on the WAN. As the design was completed, it was later realized that the available system bandwidth was far less than what was originally identified.
  • The second issue was identifying the most appropriate communications equipment to use once knowing the actual bandwidth limitations. This was an opportunity to illustrate how good project relations can methodically address project "surprises. " The design, based on the initial understanding of the bandwidth limitation, was to use MPEG 2 compression to convey video over the Commission's WAN. (At this time, MPEG 4 was a new technology and was not considered.) Therefore, a decision during construction to utilize MJPEG compression was made to convey the video images over the WAN, since it met the reduced bandwidth needs while providing satisfactory video images. This decision was made early enough in the contract that the manufacturing of the CODECs had not begun. Both Contractors agreed to change to the MJPEG CODECs and the manufacturer did not change the price.
• Keep the Design Simple. The overall design of the ATIS should be simple, seeking to maximize efficiency and effectiveness, while meeting the functional requirements of the system.
  • As an example in this project, the Commission requested a Truck Rollover Warning System, in which trucks entering a tight radius curve could be warned. The Commission was not looking for a weigh-in-motion (WIM) capabilities, headway measurements, height measurements or full vehicle classification data. System operations and maintenance determined that a simple system comprised of solid state switches and relays would be the best solution. In the end, the simple solution has been operational without a flaw, whereas other similar systems within the State, with multiple functions, have been out of commission due to their intricate operations and maintenance requirements.
  • Another example of keeping the design simple was to start with a baseline software system. It was determined by the project team, that it was easier to start with something existing and then modifying it to the needs of the Commission. After a competitive selection process, the existing MIST® software platform was determined to have the most common functionalities required by the Commission as the baseline software. Modifications were made to the MIST® software to incorporate the customization required by the Commission.

Based on the PA Turnpike Commission's experience with their ATIS project, a number of key lessons learned were developed regarding the design of the system. Defining agency needs at the outset, understanding the limits of the communication system, and keeping the design simple are steps that can be taken to facilitate a successful design phase. Through adequate design, the agency can maximize the operational efficiency and effectiveness of the system in order to achieve the desired safety and mobility benefits.