Oswald's Corner. Comments on recent. autism-related research reports. A Revised M-CHAT. A paper by Robins et al. appeared in the January 2014 issue of the journal Pediatrics, reporting the first. published data for a revised version of the Modified Checklist for Autism in Toddlers (M-CHAT) screening.
After the ride starts, Uber does indeed charge for waiting time. However, the charge to the rider is often less than the minimum wage, and what the driver gets is only 72% to 75% of that. For example, on an UberX ride here in Utah, Uber charges you $.11/minute ($6.60 / hour) for wait time. I would get $4.95 of that.
You cannot book Uber ahead of time - you have to use the app and request when you are ready. In the request you'll be able to see the expected wait time. I have not used Uber at IAH (since I live here), but in othe cities the wait has been minimal and the fares are always comparable to taxis.