This paper studies the longitudinal development of a vowel timing alternation known as the “Scottish Vowel Length Rule” in a distinctive variety of Scottish English spoken in Glasgow by working-class men and women. Combining apparent-time and real-time evidence, we show that the implementation of the Rule has changed over time, though unlike in many other varieties of Scottish English, the factors shaping its fate seem to be internal rather than external. Overall, Glaswegian English behaves like a quantity language and controls for prosodic timing effects while preserving the phonological timing alternation; and this is despite a marginal, quasi-phonemic status of the Rule
