Simone, like admin I do not understand your point. Although it does not reflect the views of every member of the party the "gridlock" comment appeared in an official Libdem newsletter published, I believe, by the local constituency association.
I find it rather sad since the party has a reputation for taking the high moral ground on many issues but, in this case, they are being manipulative. "Gridlock" is an emotive word applicable to traffic paralysis. It is printed in bold in a large font and appears to be the word that the author wishes to impact on the reader, perhaps to play on their emotions rather than their reason.
Would Marple be paralysed as a result of this development? It seems unlikely but we need more information before reaching a conclusion. The only estimate I have heard is 240 traffic movements to and from the store at peak time on a Saturday. That is just 2 vehicles per minute in each direction which doesn't seem too horrendous, especially when you consider that some of those vehicles will head south from the store, away from Marple. Marple's traffic problems are largely confined to the morning and evening rush when supermarket traffic would, I suspect, be much lighter.
I think deliveries might be more of an issue but, unlike some politicians, lets wait and see.