But is that really the case?
The first motorway bus lane opened in October 1974, and is still open today.
I can see the incredulous looks from here. What on earth are you babbling on about?
In 1973, the M63 Sale Eastern and Northendon Bypass was under construction, but the construction of the junction with the A5103 Princess Parkway involved moving a bus stop. The new bus stop, with an appropriate lay-by was happily provided (and indeed is still there today, if you know where to look), along with the footpath required to access it. Unfortunately, objections came across the desk at the Ministry, as this bus stop was in the middle of the junction complex, quite a lot further away from the nearby housing than the original bus stop, and involved the use of a subway. It was upheld, and in November 1973, the a Variation Order was published, and design was changed to make the footbridge between the two parts of Yewtree Lane (just to the south of the junction) actually useable by 1970s standards at least, with better gradients for pedestrians included. As well as that, it was always within the junction design that it would be possible to later add a route for buses to go around the junction rather than through it along Princess Parkway; and it was decided to bring this forward.
A second Variation Order was published in April 1974 in order to add the new bus routes to the junction layout, and the notes read:
Now, these notes make clear that the bus routes provided are all-purpose and not Special Roads, but there's a little more to it than that.In making the M63 Sale Eastern and Northenden By Pass Motorway and Connecting Roads (Side Roads) Variation Order 1973, the Secretary of State announced that he would publish a second Variation Order providing for the re-routing of northbound buses around the perimeter of the Princess Parkway Interchange, which would enable the bus stop to be re-positioned at a site which did not involve subway access. This is the Order now published in draft for public comment.
The Order provides for the construction as part of the new bus route of two new lengths of all purpose highway. The County Engineer of the Greater Manchester County Council has agreed that he will ask his Council to agree to seek powers to restrict the use of the main carriageways of these new lengths of highway to public transport omnibuses.
This Order also provides for certain highways around the perimeter of the interchange which were referred to as cycle tracks in the 1970 Side Roads Order to be designated as roads. This is necessary because the County Engineer of the Greater Manchester County Council proposes, prior to the opening of the motorway, to ask his Council to seek powers to prohibit certain classes of traffic from using Princess Parkway at the interchange. In this event the new highways around the perimeter of the interchange, in addition to catering for pedal cyclists and pedestrians, would provide an alternative route for those classes of traffic excluded from using Princess Parkway.
Let's deal with the final paragraph first. This doesn't seem to have happened - there is no signage suggesting that a TRO was ever put into place on this section of A5103, and the signage on the bus lanes also suggest otherwise, as the northern lane is simply signed as "no vehicles" with an "except buses" plate; and the southern one is signed as "no vehicles" with a plate that reads "except buses and authorised H.G.V's [sic]".
So, according to the second paragraph, the bus lanes at that location are both all-purpose, and so, whilst reasonably interesting in their own right, not motorway bus lanes.
Unfortunately, this is the point the trail goes cold. The assumption is that these bus lanes opened with the motorway in October 1974, but I can't be certain from the documentation so far found.
Except...
The northern bus lane, at this location can be seen on Google StreetView. As can be seen, this isn't signed as a motorway from the entrance, just with the "no vehicles" signage. However, it leads inescapably to a sliproad that is quite definitely a motorway - and there's a chopsticks hidden in the undergrowth most of the way along it. Just in case there is any doubt, the "no chopsticks" end of motorway signage is around a third of a mile further on. So, either there's a 1970s spontaneous motorway going on here, or that small stretch actually ended up being a Special Road. Either way, it is at the very least to all intents and purposes a motorway bus lane.
The southern bus lane, at this location, can also be seen on Google StreetView. This seems at first glance to be an open-and-shut case - there's an M60 chopsticks just beyond the split. However, just to muddy the waters, there's also one before the split. And whilst the A5103 is the responsibility of Manchester City Council, there's an obvious line across the surface where the responsibility changes to Highways England, and that also continues across the bus lane.
So, I mentioned that the documentation trail goes cold in 1974. Well, there is one piece of modern documentation that's available to us, and that's the National Street Gazetteer. The northern bus lane does not appear to be listed, but the southern bus lane has a Unique SRN of 24525392 and is called "M60 JUNCTION 5 BUS LANE NORTH, MANCHESTER", and is maintained by Highways England. Now the NSG also contains classification information, and it clearly states... Classification: Motorway.
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On a slightly separate note, there is also another road in that junction to allow local buses to pass around the junction southbound, though there doesn't seem to be such an interesting backstory with it; though it is more clearly a motorway at both ends, and is signed as such; though this time with "no entry" signs with a "except buses" plate just beyond the point where the bus lane becomes its own separate road. It's clearly at least not a motorway for most of its length, as it also carries NCN62 along it. Even more oddly, this also has an entry in the NSG (USRN 24525391), where it is also listed as a motorway...