Thought I'd do a very rough run through the numbers based on an optimistic scenario in which Northern get a version of the Sadler Flirt for their self propelled units.
TLDR; Phase 1 enough to replace 150,155,156,769 and 3 car 158s
Phase 2 enough to replace 2cars 158 and 170s
Overall units reduced by 33, carriages increased 198 and overall usable length increased by 1870m.
Edit; Number are a bit off as I assumed 8m for the power pack when they are 6.69m.
Current
Class units Cars length
150 3car x6 =18 360m[60m]
150 2car x69 =138 2760m[40m]
155 2car x7 =14 322m[46m]
156 2car x66 =132 3036m[46m]
158 3car x8 =24 552m[69m]
158 2car x45 =90 2070m[46m]
769 4car x8 =32 640m[80m]
170 3car x16 =48 1104m[69m]
195 2car x25 =50 1150m[46m]
195 3car x33 =99 2277m[69m]
Total =283 =645 =14271m
150 3120m
15x 9100m
Phase 1
Class units Cars length
MMU
Flirt 3car x44 =132 2860m[65m] {2508m minus power pack}
Flirt 4car x66 =264 5280m[80m] {4752m minus power pack}
BMU
Flirt 4car x6 =24 480m[80m] { 432m minus power pack}
Total x116 =420 8620m {7692m minus power pack}
7692m Flirt usable length
7670m replacing 150,155,156,769 and 158 3car.
Class units Cars length
158 2car x45 =90 2070m[46m]
170 3car x16 =48 1104m[69m]
Total = 61 =138 =3174m
Phase 2
Class units Cars length
MMU
Flirt 3car x30 = 90 1950m[65m] {1710m minus power pack}
Flirt 4car x20 = 80 1600m[80m] {1440m minus power pack}
Total x50 =170 3550m {3150m minus power pack}
3150m Flirt usable length
3174m replacing 170 and 158 2car.
BMU
Flirt 4car x26 =104 2080m[80m] {1872m minus power pack}
Total P2 x76 =274 5630m {5022m minus power pack}
Total cars= 694 length= 14250m {12714m minus power pack}
After Phase 2
Class units Cars length
195 2car x25 =50 1150m[46m]
195 3car x33 =99 2277m[69m]
Flirt 3car x74 =222 4810m[60m]
Flirt 4car x86 =344 6880m[80m]
Flirt 4car x32 =128 2560m[80m]
Total =250 =843 =17677m* actual 16141m
Total -33 +198 +3406* +1870m
Edit 2;
Added a mock-up of a Northern Regional version and some PTE commuter variants. Credit to WestRail642fan on Wikipedia for the original artwork.
