Elevated tracks would need to follow major road medians, negotiate tight corners and probably have a real (not perceived real due to media beat-up (Caulfield-Oakleigh skyrail)) public backlash which would be unwelcome.
The docs release to date have the Cheltenham(or Southland) to Box Hill segment with a travel time of 20 minutes... which is lightning fast that would possibly be achievable with elevated tracks up the guts of Warrigal Road or further over on Springvale Road but it'd miss connecting Monash (on a Warrigal Road route) and would probably not connect with Box hill on a Springvale Road route.
No moron is going to propose demolishing houses for elevated rail pylons so the route can be more direct and link the same amount of nodes the current stage 1 will look to do.
Based on the map of drill sites so far (via [url=https://www.google.com/maps/d/u/0/viewer?mid=16HpNWuvysZAhpH3IOkZvmvDvf8x2XE6E&ll=-37.904797014764384%2C145.13598441967545&z=14]operational incident on twitter[/url]), I did a very rough back of an envelope calculation on distance and times based on the assumption the rolling stock will perform like the Almost Metropolis trains specifically built for Sydney metro.
repost from SSC.
- Southland-Clayton section is ~8.5-9km.
- Clayton-Monash is ~2km
- Monash-Glen Waverley is ~4.5km
- Glen Waverley-Deakin is ~6.5km
- Deakin-Box hill is ~3-3.5km
20 second stops at each station + ~40 seconds to reach top / near top speed (in which you'd have travelled about ~550-600m), the Southland/Cheltenham-Clayton journey would be:
1 minute (station stop + time to get to top speed) + 6.5-7.0km @ ~100-120kph (~3m55s-3m15s) + 1 min to slow down for Clayton. Let's just say ~6 minutes from Southland to Clayton.
Clayton-Monash would probably not hit top speed, but a ~3ish minute journey.
Monash-Glen Waverley: 1 + 1m30s-1m50s + 1 (~4 min) journey
Glen Waverley-Deakin: 1 + 2-2m30s + 1 (~5 min) journey
Deakin-Box Hill: 1 + 1-1m15s + 1 (3.5 min) journey.
6 + 3 + 4 + 5 + 3.5 = 21.5 minutes end to end. Note I know I've double-counted stopping time (2 x 20 seconds) at stations - it's padding and there's probably other areas where there's padding too.
Pretty close to the maps on Strategic Assessment docs.
In short: no elevated route is going to link as many nodes nor as fast as the underground route.