Thank you for your thoughts.
I don't believe this can be true. If the dynamic model is used in the code, then it would still be possible to use the current static costs by setting all the dynamic (i.e. new) costs to zero. We are not throwing away the existing cost mechanisms, merely adding new ones that can be used in parallel.
It is a little more complex than that: the current code does not distinguish between maintenance cost and fuel costs. The plan is to have maintenance costs and fuel costs separated and then governed by different rates of inflation; so the code needs to be updated in any event.
What I was referring to in the passage quoted was not so much the need to replace parts of the code, but rather the fact that, without modelling both dynamic fuel consumption and dynamic fuel efficiency, modelling dynamic fuel consumption alone is likely to lead at least in many significant cases to less accurate average fuel consumption than simply modelling average fuel efficiency. There are some particular problems with this: firstly, it is fairly easy to find averaged fuel consumption data for a range of vehicles, but very difficult to find such data in a way that correlates these data with power output.
Secondly, there is a particularly important aspect to dynamic fuel efficiency which in reality has a very significant impact on vehicle selection, which is this: a high power output vehicle will tend to be much less efficient at lower power outputs than a low power output vehicle. Not simulating this fact may well render useless a large range of low power output vehicles that are useful in reality precisely because they have better fuel efficiencies at their intended, lower power outputs. One of the things that I am especially keen to avoid is the situation that exists with Standard in which players have an incentive always to use the most powerful vehicle for everything. If there is no cost to using an overpowered vehicle, it would be difficult to avoid this. Even peripheral means of incentivising the use of lower powered vehicles (higher capital cost and weight) are likely to be insufficient in a significant number of cases, particularly with rail vehicles where these factors are likely to be less significant in many cases. In reality, there was a reason that huge heavy freight engines were not also used for suburban passenger work.
If there are any cases where a completely static model truly is better than the simple dynamic model, then we can continue effectively using that.
There are two problems with using a case by case approach to determine when it is better to use a static rather than dynamic fuel consumption system: firstly, it is likely to be difficult to work out which vehicles fall in which cases, and secondly, it is likely to be very confusing for players for fuel consumption to vary with power output in some, but not all, cases. The first problem in this case exacerbates the second.
This get-out might not work for trains, but I think trains are where the simple dynamic system will give the greatest improvements over the static system. Indeed, I don't think you have responded to my scenario in reply #34 (cost savings due to switching to a more efficient locomotive should be greater for longer/heavier train).
My apologies for not having dealt fully with this earlier. For ease of reference, I quote the relevant parts below.
I think it is currently impossible to produce accurate (or close to accurate) running costs for all four combinations of:
1. A diesel locomotive with high energy costs
2. An electric locomotive with low energy costs
and:
a. A short train of (say) 2 coal wagons
b. A long train of (say) 20 coal wagons
Clearly replacing 1b with 2b should lead to a greater reduction in running costs than replacing 1a with 2a, but at present these two replacements cannot produce different reductions in costs.
So this suggests that some account of actual energy consumption is needed in the long run.
The comparison is valid, but the real question is whether a dynamic system can be implemented in which the overall adverse effects of implementing it are less than the sub-optimal state of the improvement in energy costs of upgrading from diesel to electric in the above example being less differentiated than they would be in reality.
The biggest problem is the lack of effective data available as to dynamic fuel consumption and its relationship with power output; if, for example, a particular 'bus is recorded as having an average fuel efficiency of 4 miles per gallon, how can that datum be used to calibrate a dynamic system? As somebody who needs to be able to balance the pakset, I have to have a reliable way of extrapolating from fragments of real life data, and I see no way of doing that with the available data for a dynamic system.
The second biggest problem with a single dynamic system is that described above as to the perverse and unrealistic incentives created by having non-dynamic fuel efficiency. In practical terms, those adverse effects would appear to create incentives that deviate more significantly from reality than the incentives created by there being insufficient difference between energy cost savings of high and low power output situations.
I think the best way forward is to modify the code to allow for dynamic running costs, and then try them out. If it does turn out to give worse operational costs, then we can revert to the current model without any further changes to the code (perhaps even leaving dynamic costs as an option for other paksets).
The trouble with this approach is that that modification to the code would take a truly gargantuan amount of work (the physics engine is fantastically complex and I did not write it, so I have little understanding of how it works), so there has to be a very, very high chance that this will be very significantly better than a static averaged system to justify doing this work. I would also need to be very confident that it would be possible to get sufficient real life data to calibrate a dynamic system at least as well as a static system could be calibrated before coding for this.
What I had suggested in a post some time ago was dry run testing - mathematical extrapolation of various cases without modifying the code to test in principle whether either of the three theoretically possible systems, being (1) static averaged; (2) single dynamic; and (3) double dynamic would be viable.
As stated, unless we can actually find a way of overcoming the three obstacles to a dynamic system, being
(1) the difficulty in creating a workable algorithm for a double dynamic system, or alternatively, the perverse incentives generated by a single dynamic system;
(2) the possibly excessive computational load of having to calculate fuel consumption dynamically; and
(3) (probably the most problematic of all) the lack of data enabling a dynamic system to be calibrated,
the only sensible way forward that I can see is to implement the static averaged system.
Edit: Incidentally, an additional thought in relation to the issue raised in post no. 34: in most cases, a player hauling a small load would be more likely to choose a low powered locomotive over a high powered locomotive capable of hauling a large load. Thus, in the situation where the player is using locomotives with different maximum power outputs in each pair of the four cases given, the fuel cost saved by the player will be greater in moving from the high powered diesel locomotive to the high powered electric locomotive than from the low powered diesel locomotive to the low powered electric locomotive.
