<P> One such distinction is that between these systems and older British / English units / systems or newer additions . The term imperial should not be applied to English units that were outlawed in the Weights and Measures Act 1824 or earlier, or which had fallen out of use by that time, nor to post-imperial inventions, such as the slug or poundal . </P> <P> The US customary system is historically derived from the English units that were in use at the time of settlement . Because the United States was already independent at the time, these units were unaffected by the introduction of the imperial system . </P> <P> British law now defines each imperial unit in terms of the metric equivalent . The metric system is in official use within the United Kingdom for most official applications with Imperial units remaining in widespread use amongst the public . All UK roads use the imperial system except for weight limits, and newer height or width restriction signs give metric alongside imperial . </P> <P> Units of measurement regulations require all measuring devices used in trade or retail to display measurements in metric quantities . Almost all traders in the UK will accept requests from customers specified in imperial units, and scales which display in both unit systems are commonplace in the retail trade . Metric price signs may be accompanied by imperial price signs provided that the imperial signs are no larger and no more prominent than the metric ones . </P>

What form of measurement does the uk use