public transport systems. The signals can be set up to sense the approach of buses or trams and change the signals in their favour, thus improving the speed and efficiency of sustainable transport modes. Obstacles to widespread introduction The main stumbling block to the widespread introduction of such systems is the fact that most vehicles on the road are unable to communicate with the computer systems that town and city authorities use to control traffic lights. However, the trial in Harris County, Texas, referred to above, uses a simple system based on signals received from drivers' cell phones, and it has found that even if only a few drivers have their phone switched on, the system is still able to produce reliable data on traffic density. This means that the adoption of smart traffic lights around the world could be started as soon as a reasonable minority of vehicles were fitted with the technology to communicate with the computers that control the signals, rather than having to wait until the majority of cars had such technology. The first experiment In July 2019 the first experiment of a traffic signal regulated by 100% "connected" vehicles was carried on at University of Calabria (Unical) with the help of common commercial smart phones by a team of researchers working for Unical and the innovative Start Up SOMOS. Simpler systems In the United Kingdom, lights that changed to red when sensing that an approaching motorist was traveling too fast were being trialled in Swindon in 2011, to see if they are more effective at reducing the number of accidents on the road than the speed cameras that preceded them and which were removed following a council decision in 2008. These lights are more focused on encouraging motorists to obey the law but if they prove to be a success then they could pave the way for more sophisticated systems to be introduced in the UK. Previous research In addition to the findings of the Romanian and US researchers mentioned above, scientists in Dresden, Germany came to the conclusion that smart traffic lights could handle their task more efficiently without human interface. See also Traffic light control and coordination Level crossing Pedestrian crossing Scalable Urban Traffic Control Traffic optimization References Smart devices Traffic signals