For those of you who use Investor R/T software, you have a choice on how you break down volume, the Mister Ed version (bid/ask) or my version (uptick/downtick). Here is a quote from their site:
http://www.linnsoft.com/new/index86.html
The Volume Breakdown Indicator (VB) has been enhanced with an option to divide up volume by "Up Tick vs Down Tick Volume". In the past, volume was always broken down between Ask Traded and Bid Traded volume. Now, the user has a choice of dividing up Buy and Sell volume as either "Ask Traded vs Bid Traded Volume" or "Up Tick vs Down Tick Volume. When "Up Tick vs Down Tick Volume" is specified, each trade that occurs on or after an uptick is placed in the buy volume category, while any trade that occurs on or after a downtick is considered in the sell volume category.