The limited availability of space in urban centres prevents the extension of existing infrastructure and, with continuously increasing mobility demands, requires solutions that will alleviate serious congestion problems through the best possible utilisation of existing infrastructure.
This calls for the employment of the most efficient actuated systems that respond automatically to the prevailing traffic conditions so as to avoid oversaturation, increase throughput, and reduce travel times in urban networks. A number of real-time (traffic-responsive) urban control strategies currently exist.
These strategies, however, suffer from two major disadvantages. They do not directly address saturated traffic conditions, and they are functionally decentralised, basing signal-setting decisions for each junction on the current traffic state in adjacent streets only. In addition, several of the currently available strategies require specific real-time measurements, or complex implementation software, limiting their easy transferability and increasing their implementation costs.
SMART NETS aims at enabling a significant improvement of the international state-of-the-art in real-time network-wide urban traffic control via application, demonstration, and comparative evaluation of the new-generation control strategy TUC (Traffic-responsive Urban Control).
TUC employs advanced automatic control methodologies which may lead to improvements in the order of 40% of journey times as compared to fixed-time settings under saturated traffic conditions where all current signal control strategies are known to perform poorly.
Within SMART NETS, TUC will be extended to consider public transport priority measures. The demonstration will be conducted in extended network parts of Southampton, Munich and Chania, and include field-comparisons with the current resident control methods (SCOOT, BALANCE, TASS). A successful completion of SMART NETS would mark a new era in urban traffic control worldwide, with substantial technological and economic impact for European ITS activities.
The first stage in SMART NETS was the design and testing of TUC for the three demonstration sites and the inclusion of public transport priority in TUC.
At this stage extensive simulation investigations were performed under different scenarios, e.g., of demand, incidents and device failures, and based on various criteria, such as average journey time, throughput, saturation levels and fuel consumption. The outcome of this stage was the design of the TUC control law and the preliminary assessment of TUC's capabilities for the three application networks.
This was followed by the field implementation and verification of the strategy in the three test sites. The same generic software was implemented in all sites, with the particular topologies and traffic conditions reflected in corresponding individual input files for each network application. This demonstrates the transferability and easy applicability of TUC.
Finally, and currently underway, are the field demonstrations. Analysis of data collected during demonstration in the three sites will allow the assessment of the impact of TUC in each site, as well as a comparative evaluation of the operation of TUC across all sites.
Evaluation will be performed according to the SMART NETS Evaluation Plan, which was developed at an early stage of the project.
SMART NETS' main contribution to the state-of-the-art was the provision of an easy-to-implement, inter-operable, easily transferable traffic control strategy that can provide a very efficient performance with a minimum amount of fine-tuning. In this way, the project has significantly contributed towards the development of an innovative traffic control strategy that can be easily and quickly implemented and can provide a significant reduction of travel times within urban traffic networks.
The performance of TUC has been evaluated in all three sites -Cahnia, Southampton and Munich- and compared to the three resident systems - TASS, SCOOT and BALANCE respectively. TUC performance in all the test sites demonstrated that it is a valid and credible UTC strategy, both as a stand-alone system and as a hybrid.
Although the demonstrations did not show the same level of improvements as had been achieved by TUC in simulations, where it had been compared with simple fixed-time control, TUC stood up very well against the well-established and sophisticated resident systems in the three cities, and user acceptance was generally high.
One further very important finding from the demonstrations is that TUC can perform well in any type of network: the five test areas in the three cities have very different characteristics, both with regard to network layout and with regard to traffic behaviour. This allows the conclusion that TUC can be successfully implemented in any other site in Europe or elsewhere in the future.
Overall, the SMART NETS project has demonstrated that TUC has the potential to become a strong competitor in the worldwide UTC systems market.
A strong co-operation between traffic control engineers and researchers from different European countries has been established through the project, which has had a significant impact on the identification, analysis and – in many cases – solution of a variety of problems that occur in traffic control applications. The core of SMART NETS was not only the demonstration of the TUC system, developed by the Technical University of Crete, but also the comparison of its performance with other established systems, such as SCOOT, the traffic-responsive UTC system developed in the UK and BALANCE, from Germany.
A key element in SMART NETS was the User Group, with representatives from ten cities in seven European countries, which were invited to formulate their requirements for urban traffic control and the resulting conditions that TUC would have to meet if it was to be introduced in their networks. This international co-operation was designed to ensure Europe-wide compatibility of TUC with existing UTC systems and strategies and, thereby, to greatly enhance the prospects for widespread exploitation of TUC.
SMART NETS addresses a whole series of EU policy issues, most prominently some of those addressed by Key Action I of the Fifth Framework Programme of Research, by aiming to provide an innovative system that improves services to the citizen and strengthens the European position in the global ITS market. SMART NETS specifically addresses policies described in the Commission communications: 'Community Strategy and Framework for the Deployment of Road Transport Telematics in Europe', 'The Future Development of the Common Transport Policy', 'The Citizen's Network', and the 'Directive on Air Quality'.
The three demonstrations of the TUC system in SMART NETS have proven that there is enormous scope for the exploitation of the current results and further development of TUC. A number of recommendations have been made for future TUC implementations:
- The first recommendation relates to the existing TUC implementation in Munich since the detailed analysis of the available data for the impact assessment was, unfortunately, inconclusive, with large variations between the two sets of week-by-week comparisons. Since both BALANCE and the BALANCE/TUC hybrid are now available for the Haidhausen area, and both appear to provide overall a good level of control, it would be desirable to let them operate in turn over the coming months and to observe whether any firme