During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates.
dˈʊɹɹɪŋ ðɪ ˈɜːli ænd mˈɪd twˈɛntiəθ sˈɛntʃɚɹi, wˌɛn tˈaʊn ɡˈæs wʌz pɹədˈuːst, kˈoʊl tˈɑːɹ wʌzɐ ɹˈɛdili ɐvˈeɪləbəl bˈaɪpɹədˌʌkt ænd ɛkstˈɛnsɪvli jˈuːzd æz ðə bˈaɪndɚ fɔːɹ ɹˈoʊd ˈæɡɹɪɡˌeɪts.