Bucki, have you considered what makes this easier for you than the "most commonly used" way of boarding the busses with the ramps? For instance, some of us can very easily navigate driving backwards while making a left turn, but not while making a right one. In those situation it would only be wise to board accordingly to those abilities where ever possible. If it takes some more time; so be it.
I also know for some people the....... "being watched" and having others on the bus while driving off can get into their had. In that case, I'm one of those persons that says; ignore those people! As if they always do everything perfectly.

Worried about feet sticking out you (in general) might hit? Look around before starting the process of getting off and kindly ask if people could temp. move out of the way if you worry about them being too close for your comfort or (everybodies) safety. This tends to go a long way, esp. when you use some humor while doing that.
For others, it's just plain anxiety about not being able to get out of the spot after boarding and being "stuck". That won't happen as there will always be somebody willing to help out in sticky situations (incl. drivers that have helped with
ECV's getting on and off in the past). In those cases it can help to practice in parrallel parking and getting out at home. Using some plastic cones or something to outline the spot on the bus and the ramp and practice. Not only can it help boost confidence it also is a great insight into what small things might get one into trouble and where there is lots of room for movement left when it didn't look like it while driving. This can be a great help in making those movements a lot easier.
Either way; communicate! Be open and honest and talk about what you need or desire. That tends to go the furthest with drivers and other guests alike (both those walking and others using a mobility aid waiting inline with you). To give you an idea; if I'm "second" in line for the bus and find another guest in front after me with an ECV for the same bus? The bus arrives and we find there are 2 handicapped spots left. In those cases I'll suggest the ECV-user boarding first but into the second spot, more to the back. It gets some

at first sometimes but when I explain that with an ECV that is the easiest spot to navigate and I can easily park my powerchair into the front spot after that, everybody appreciates the idea. For me it also works multiple angles. Also boarding first allows them the "most" space to move around while parking with an aid that has a much larger turningradius than my chair does.
Truth be told, I also do got an eye out for ECV-drivers in those tight situations. With so many rentals you never know who's a practiced driver and who isn't. In those relative small spaces it can happen that a wrong turn is made or a bit too much speed is used and things get knocked into. Those can just happen, that's life but I try to be proactive on it for both egotistical motives and not (I know it doesn't feel anywhere near peachy when knocking into something with even the slightest of knocks).
It depends on the type bus you get. The older WDW buses (the ones with steps that lower and then flatten out), require you to back in
Actually, they should do this based upon where the mainweight of the aid being used is located. While it is most common for aids in the US/seen at WDW to have said weight in the back and it thus only making safe to board while backed up onto the lift, if the aid has other criteria safety and training requires the driver should only allow boarding that calls for safety. Having said that, some drivers have a hard time with understanding this.
I happen to have a powerchair with the mainweight in it's front, requiring it to drive straight upto the lift instead of backing up when loading. Has caused some discussions (most resulting in CM's giving me the "what an annoying know-it-all-she-is"-look but allowing me to board as is safe with my chair) and in some situations causes drivers to refuse me. I've had supervisors on the spot more than once as I always -nicely- make a big stink about this. It's one thing to "just" refuse me, it's a totally different thing when not working in a safe way. Each of those times I've been told by supervisors that indeed policy calls is as I mentioned above and some drivers need a bit of retraining on this subject instead of blindly trusting it will be one of those daily common situations. Upside; the extra bus called in after a refusal and having a supervisor on the spot tend to all have been the greatest drives I've had on property. Met some of the nicest, most upbeat and amazingly skilled drivers that way.
