Topic: Vehicle Transportation Model (How to calculate % survival profile)Subscribe | Previous | Next
Jamsheed Sajid 11/5/2020
Hi all
I am jamsheed Sajid Currently working as a research scholar at USPCAS-E NUST Islamabad. I am facing an issue in my transportation model which is that my % device stock goes down from the base year till the years which i have used as life of the vehicle ( total years for which i have given the survival profile data) and after that time the stock values goes Up till the last year. For example, if i have 2010 as base year and have given life of the vehicle till 2022 while final year is 2040. now the stock goes down from 2010 to 2022 then goes up till 2050.
Please guide me about that point. is there any issue in my life cycle profiles?
one thing more is that is there any specific formula or Procedure to calculate % vehicle survival profile? Please guide me for that step as well.
Charlie Heaps 2/18/2021
Hi Jamsheed,
Its sounds like your model is retiring vehicles faster than new vehicles are being added in the first few years of your model, but later on as total sales grow the sales overtake the retirements so that total stocks eventually start to increase.
So this may suggest that your retirement profile is too fast (too aggressive). The default data in LEAP's transportation examples tends to reflect the situation in OECD countries where cars have fairly sort lives. You may want to stretch out your retirement curve so that cars survive longer (i.e. they get retired more slowly).
Unfortunately, I don't know of any simple formula that can translate average vehicle age into a retirement profile. If anyone know of a simplified approach please let me know and I will add it in to LEAP. However you can easily adjust these curves by specifying them as exponential curves and then adjusting the constant up or down.
Good luck!