One of the key issues that HS2 tries to address is conjestion in the southern end of the west coast main line (WCML) , south of Rugby towards London. This is a function of three main contributing factors, given that current track bed is considered a fixed constant
1) Number of trains (including freight of course)
2) Average speed of trains
3) Capacity at main passenger termini and other "nodes"
HS2 has one main aim and a couple of side effects or co-benefits: the main aim is to decrease passenger travel time on a dedicated high speed route with no other trains that those. The side benefits are that passenger capacity increases and has a new higher ceiling for potential growth, and that freight can grow on the existing WCML.
These are all admirable strategic goals of the Railway, especially as rail freight is becoming more economically attractive in terms of road haulage prices and British businesses competing by scale. However HS2 may be a very expensive way of addressing theses issues and other solutions must be considered. We cannot have a "Gulf War" bull strategy - there must be alternatives considered in a democratic country.
Let us not forget that HS1 took 13 years to build after the channel tunnel itself was complete, and that is only 67 miles (108 km)! It also went over budget and required nationalisation to actually deliver the route. The comparison has always been drawn to France and Germany: The TGV was a typically gaulish, grandoise plan in a country with a long history of strong central government with little respect for landowners. HS2 takes prime real estate in London, the Home Counties and Cheshire plus land from industry, farming and country estates.
So despite "new build" having an allure of green/brown site cost savings, and little or no disruption to the WCML , it will most likely go over budget due to land aquisition costs, unforseen geographical challenges and the inflationary pressure such a capital project will place upon civil engineering supply in the UK and on an EU basis.
Addressing the Issues Differently.
Rather than take a very discursive route further, here are some of my own proposals per issue to solve
1) Build Up, Under and Outwards.
HS2 could well have a new terminus, or use a swathes of London in connecting to the most prefered corridor north through the home counties. This causes massive disruption to all sorts of transport !
So rebuilding in particular Euston on multiple levels with several levels of track being stacked further out of the station. Also some degree of overhead avoiding loops can be built, such that local trains can be as the saying goes, side-lined, in order for expresses to accelerate out of Euston or have a higher average speed on the sections in over. Also these can be used for stacking ECS movements - relieving the carriage depots and platforms.
This is viewed as highly disruptive and highly expensive. However the capacity can be phased in, such that upside capacity like an extension sideways or outward platforms or an underground element be built at low disruption and then supplements the earlier capacity when other platforms are then demolished to build up and downwards.
2) Dont' take all Capacity into London- Where do People Want to Eventually Arrive ??
Where are all these central london routed passengers going as the end of their destination? In rush hour of course a high proportion of travellers on express trains are on business or actually long distance, "red eye" commuting. However many of those are going to locations in west, north and east London or the business hubs in the home counties.
Here then we have various solutions
a) Stack- Hub- piggy back : here you run some high speed services which terminate at outlying stations which act as hubs for travel to both the centre and then utilise the local services around London from places like Watford gap. This then decreases the final volume on the route's end, but it does not in itself reduce that much and may contribute to volume conjestion north of these points and also "platform waiting, crew change, points and shunting" congestion at those hubs as the trains have to in most cases, reverse out or find sidings.
Another way of reducing lower speed congestion while using this principle is to piggy-back in commuters on express services. This is done by taking advantage of some "yellow signals" which are in the diagram for an existing or proposed service- where an express encounters a slower train some miles infront of it, before that train enters a side platform, as siding or diverts off the WCML. So in this approach an express train calls at a key commuter station, like Milton Keynes.
A consideration in planning this is also to move people on trains NORTH to places like Milton Keynes in order to meet express services and actually reduce their journey time southbound. This way trains run counter congestion as feeder-hub services.
b) Build More Round London and Improve Inter-Transport Stations
Britain still lags far behind most of Europe on integrated transport. We had a big lead in the earlier metropolitan projects like the London Tube and in the Glasgow Area in particular, but we still lack the joined up writing in getting people swiftly and comfortable over to another transport mode, and having that transport mode have a gauranteed connectivity or good frequency.
There are several lines which run around the North and West of London in particular and some other diagonal corridors which can be expløoited and maybe double-decked or have new transmodal transport stations built at their intersections or have new chords intersecting them from main routes of all public and indeed private transport as in park-and-ride stations.
Also ignoring the London Metropolitan Area Commuter, many travellers are pretty much well forced into the terminii by ticketing or timetabling in order to affect a route out again to places further a field. This should be addressed not only by the hub approach, but by encouraging faster connecting services on other routes south of Birmingham, and more services which cross the main great rail corridors, Western, Oxford, WCML, great central, ECML and great Eastern.
For example for anywhere in Berkshire, Buckinghamshire or East Anglia, you should not need to nor be forced by cheapest ticketing to go through central London Terminii both in commuting times with arrivals before 0930 and through the day. You may have to change trains at a hub in the north, but your overall journey and transfer time should be similar if not reduced.
Number Of Trains
I touched on above that it is not just the number of trains, but the type of train of course, so the next issue, average speed is largely now a function of the slowest train in the "bottle neck".
Volume of traffic is addressed immediately by having longer trains towards maximum legnth possible for the stations on the route, and then of course lengthening stations! This has been an approach taken around London. You can then also hub people into fewer, longer, faster trains as mentioned above and those small 3 to 6 carraige trains get supplemented and replaced by longer or faster express and semi stopper services.
On these longer piggy back services, you then really need to plan and actually lock seating capacity in for those commuters: this can mean ticket management with booked seats to cluster shorter journey travellers, or those leaving at the hubs for new trans-services, into the same coach such that they are emptied for the new commuters ready to board; or closing carriages off for the whole journey: Or merging trains with new ECS at the hubs.
Merging trains is less time consuming that it was before and capacity at "hubs" or other stations or sidings could be made such that also several slower stopper commuter services can merge into a single non stop service to the terminii.
Now we have only so far talked passenger:, what about Freight ?
A key strategy for governments is to react to the end -of-oil time which will be facilitated by global warming if we choose of course to ignore the new-ice-agers sponsored by the main producers. Another issue is grid lock on motorways and finally as above, an economic pressure for more supply for rail freight.
Freight is slow in two ways: average speed and pick up times to peak speed / optimal speed from signal haults. Also freight is getting longer, which is a problem when you consider injecting more signal sections into some parts of routes in order to stack in more short passenger trains. But that is not the issue with length- the main issue is when they leave the main line and have to cross left to right from sidings - they block then double the capacity they use - the old line, the new line, and the line in the opposite direction is affected if the freight crosses to exit the line.
So to .....
Average speed then in general : In theory there is a max capacity, zero speed where all the sections of line are used up- not quite end to end trains but trains with their protection of seperation zones. You can then increase the number of sections and decrease average speed to push more trains along- in other words the queu would at least move. Conversely then to increase average speed for trains capable of high top speed and safe stopping distances, you have to increase the length of each section.
By in large this sectioning of the WCML has evolved over time to a perceived optimum, or at least a compromise between the needs of "compressed" capacity as you reach the terminii and the elastic speed outside.
So in an ideal world the trains move at a reasonable average speed towards the terminii where express and local must share: local accelerate fast enough to the peak speed and then are off on side lines with a level of separation which just slows the express to a lower speed, or are dealt with by a speed limit to make sections work smoothly and with higher safety margins than are really needed.
Throw in freight. It is slower and means that section length has to be managed for the expected legnth of freight and that faster trains behind that have to be able to stop ( which goes without saying actually.) But this reduces capacity at a lower average speed as well as slowing speed up the line due to "yellow" warning signals lasting longer and more red signals being met by expressess with a slow freight, yet still actually moving, infront of them.
A lot of freight even on the electrified WCML is diesel hauled due to this being economic in terms of "rail head" pick up delivery where shunting, or low speed creeping off loading is now most often conducted with use of the delivey locomotive. Diesels are not as reliable as electric locomotives today, with failures being rare but time costly problems. However at key speed ranges diesels can be slower to pick up to maximum speed than electric locos
When you have then a practical number of sections and average planned speeds are known, you eventually reach this capacity issue and have to slow down the whole route to allow in particular, more freight to run. The combination of profitable high revenue freight and more commuter services have in effect negated the advances made in tilting trains that can operate over 120mph, and we are stuck with journey times you could have seen in a 1979 timetable for many services.
An Alternative - Low Speed 2!!!Among the different proposed routes for HS2 has been a "Marlyebone" corridor north to Aylesbury and through Oxfordshire from Thame possibly . There was existing track bed here and along the Chilterns route which is still in operation. Rather than building much parallell line to existing then, the route could be developed to deliver mostly freight traffic at lower speeds to the NW of London and round the South to Southampton in particular as a major port, and the Channel Tunnel.
There could be new line south of Birmgham connecting to the chiltern line, and some broadening of this line in rural routes to four track. On this then freights of different speeds can pass and all freight can be priortised such that journey time to the outskirts of London are actaully improved over the WCML. Nearer to london then, where space is at more of a premium, avoiding sidings could be made so that the passenger routes that share this can avoid some of this.
Second to this, a new wide west of London avoiding line should be made, which has the advantage of crossing over several major, radial lines at speed while having junctions onto them as well, while also being then interconnected to the whole SE network south of London more quickly than current progress over London.