A wnaiff Llywodraeth Cymru gyhoeddi data ar lefelau tagfeydd cyn ac ar ôl gweithredu'r polisi 20mya diofyn?
Wedi'i ateb gan Dirprwy Weinidog dros Drafnidiaeth | Wedi'i ateb ar 03/06/2026
There is currently no official pre-20mph congestion data available, which means that a pre- and post-implementation analysis of congestion levels cannot be carried out at this stage.
However, the default 20mph speed limit national monitoring report, published by TfW in July 2025, found that journey time reliability had improved on the roads they monitored, and generally more reliable journey times can be an indicator of less congestion.
(Saesneg yn unig)