"On this day" reminded me of the opening 136 years ago today (1st October 1890) of the Queen Adelaide Loop at Ely, allowing train arriving there from the direction of Peterborough to carry on towards Norwich with carrying on into the station and having to reverse there. In the days of locomotive haulage that was a faff, and with unfitted freight trains a double faff.   For all the issues with multiple units raised by some members, the savings made by many of these loops melted away.

I have listed here ten historic loops and avoiders - no two the same, still existing (not sure about Queen Adelaide thiough) but some only just.

Westbury East to North
Rhubarb
Mainadee
Queen Adelaide
Reading (West to Didcot)
Foxhall
Norwich Avoider
Rose Street Curve
Laverstock
Frome avoider
Cannon Street

And here are a further 10 places where loops could have been a huge benefit - including one or two installed in my living memory.

Coombe Junction
Bourne End
Bere Alston
Cromer
Battersby
Morcambe
Georgemas
Fort William
New Holland
Bacon Curve

What have I missed?   Should any of those not count?

 

Barrow-in-Furness Station - The Park South Line

Swansea - The Swansea District Lines

Two that just popped into my head

 
Cheltenham Loop, also known as Cheltenham & Gloucester T Loop, and now known as Gloucester Avoiding Line.  Opened in 1847, closed in 1851, reopened in 1901 and continues in use.