Is it correct to equalize investment commitments (CAPEX) with net debt?

I'd like to find a right multiple to compare some airports in my country. I've come up with a multiple - EV/PAX (annual passanger traffic), however EV here isn't exactly the Eneterprise Value, it's more of Invested Capital. It consists of equity, net debt and Capex (either forcasted or obliged, I'll explain). So basically I am saying that this capex is a necessity (liability) and I'd like to treat it as net debt. Can I do so?  

There have been a number of privatization deals in my country set up by a regional governments that were selling their assets (i.e. airports). Investor would pay for equity (sometimes very little) or it would be a concession. Also there'd always be a capital commitment to build / renew the current infrastructure. This CAPEX is usually much higher than what's paid for equity. Is it OK to treat it like net debt? If so can I simply calculate EV (for multiple purposes) of such deals by adding CAPEX and actual net debt to equity?