The Obstacles and The Solutions

This section discusses a few technical obstacles encountered during the initial deployment and how these obstacles were addressed.

Obstacle 1: Interference

Given the frequency band requirement, the team only has about 2 MHz to work with.  In addition, this 2 MHz space does not belong to electronic toll collection exclusively; it is shared with any other technology that uses an unlicensed transmitter.  One of the biggest issues to solve is interference, which could greatly affect the system’s performance. 

Solution: SSI’s Titan reader conducts an over-the-air analysis of the environment and adapts to it dynamically for optimal performance.  Titan actively listens to co-channels and adjacent channels and decides how to maximize throughput and communication patterns. This cognitive algorithm allows Titan to reject interference and maximize reading performance.

Obstacle 2:  Accurately Identifying Vehicles

With traffic and vehicles that are bumper to bumper, side by side, changing lanes or next to buses or trucks, the more reliable reads toll operators can get while in the read/transaction zone, the higher the chances of a successful transaction.  For instance, taller vehicles, such as trucks and buses, cause problems in the reading sequence as they move closer to the read-zone because they might block smaller cars. In addition, flat windshields of buses can create a challenge regarding tag transmission orientation.  With Multi-Lane-Free-Flow and Open Road Tolling at high speed, vehicle identification gets even more challenging.

Solution: Titan reader tracks transponder reads from moving vehicles by determining lane position and identifying vehicle location.  Together with optimized system settings, antenna orientation and lane setup, SSI’s overall design of the system creates an optimum read zone.  Therefore, the system can accurately identify close and fast-moving vehicles and prevent cross-lane reading.

Obstacle 3:  Irrelevant Reads

There are many non-tolling transponders on the road, e.g., tags on goods or packaging carried by the vehicles.

Solution:  SSI Titan reader features a Text Stream Interface (TSI) which allows operators to run text-based commands. In this case, the “Select” command is used to filter out non-tolling tags.

Obstacle 4: “Missing” Transactions

During the initial implementation, it appeared that the system had missed a number of transactions.

Solution: Assuming the settings and antenna orientation are correctly set, the percentage of missing transactions is minimal.  SSI’s support team was able to quickly narrow the issue down to the placement of passive UHF RFID tags.  Since most drivers in Turkey were used to DSRC transponders, which could be placed in the glove compartment, they did not understand how to properly attach the passive UHF RFID.  The toll collection company was advised to provide clearer instructions to drivers so that they can properly affix the passive UHF RFID tags.

The Results

The new system gives a success rate of approximately 99.5%. In addition to cost-saving, improving reliability and transaction efficiency, the biggest benefit of this new passive UHF RFID system is the reduction of congestion.  True Free Flow of traffic was enabled by the implementation of the new passive UHF RFID system.  Multi-Lane-Free-Flow and Open Road Tolling reduce congestion time and carbon emissions.  According to the Global Traffic Scorecard issued by INRIX, Istanbul was ranked the 33rd most congested city globally compared to the 4th in 2019.  In addition, there was a 70% decrease in hours lost due to congestion in 2020 compared to 2019 (INRIX, 2021). 

Next Steps

Turkey’s highway network is expected to expand to 8,247 km by 2035 (Turkey Ministry of Transport and Infrastructure, 2020).  More SSI readers are expected to be deployed as part of the expansion.