railways to link signal boxes. Traditionally, prior to around 1965, pole routes were built with open wires along non-electrical operated railways; this necessitated insulation when the wire passed over the pole, thus preventing the signal from becoming attenuated. At electrical operated railways, pole routes were usually not built as too much jamming from the overhead wire would occur. To accomplish this, cables were separated using spars with insulators spaced along them; in general four insulators were used per spar. Only one such pole route still exists on the UK rail network, in the highlands of Scotland. There was also a long section in place between Wymondham, Norfolk and Brandon in Suffolk, United Kingdom; however, this was de-wired and removed during March 2009. Environmental impact Utility poles are used by birds for nesting and to rest on. Utility poles and related structures are regarded by some to be a form of visual pollution. Many lines are placed underground for this reason, in places of high population density or scenic beauty that justify the expense. Architects design some pylons to be pretty, thus avoiding visual pollution. Some chemicals used to preserve wood poles including creosote and pentachlorophenol are toxic and have been found in the environment. The considerable improvement in weathering resistance offered by creosote infusion has long-term drawbacks. In recent years, concerns have been raised about the toxicity of creosote-treated wood waste, such as utility poles. Specifically, their biodegradation can release phenolic compounds in soil, which are considered toxic. Research continues to explore methods to render this waste safe for disposal. Historically, pole-mounted transformers were filled with a polychlorinated biphenyl (PCB) liquid. PCBs persist in the environment and have adverse effects on animals. See also Public utility Caber toss, a sport involving the throwing of large poles. Oppenheimer pole High voltage electricity pylon Traction current pylon References External links The Telegraph Pole Appreciation Society Article on Utility-Telecom Joint Use of Poles Many photographs Photographs of Various U.S. Utility Poles Hungarian Telephone Poles Utility Poles @ Ann's Garden Wood Utility Pole Inspection Methods A photo collection of pole routes throughout the UK and abroad American Wood Protection Association USDA Rural Development's Electric Programs GR-60, Generic Requirements for Wooden Utility Poles Electric power distribution Street furniture Pylons Electric power infrastructure Telephony equipment Telecommunications equipment Telecommunications infrastructure Articles containing video clips