Lulu Xue 8/5/2021

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Hi, I delve into the transport stock turnover function to understand the vehicle retirement pace of the existing fleet and find an interesting result:

When I set the annual new sales to zero and only put in the stock in the first year, and run the model. The interesting result is that instead of declining, the vehicle stock grows over time and, in some years, the numbers of retired vehicles are negative.
This also happens when I put in the real-world data of annual sales and stock. The number of retired vehicles are negative in certain years.

Where could possibly go wrong and how to fix this? And how to interpret negative retirement vehicles?

Charlie Heaps 8/9/2021
 

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Hi Lulu - this looks very strange. Retirements should not go negative. Could you send me your data set (backed up as a .leap file) and I can take a look. Please send to leap@sei.org. It is probably easiest to send it as a dropbox link (or similar, e.g. Google drive).