Moreover, the absence of advanced technology, such as collision warning systems, at airports exacerbates the risk.
As ATC Watcher mentions, there are systems available to warn of many things. They are often considered to be ‘safety nets’ that ‘save the day’ when normal people and procedures have failed. But it’s not just money that limits their implementation - common sense and effectiveness should also be mentioned here.
Any safety warning system needs to warn when it is necessary and do nothing at other times. Configuring systems to do this is a huge undertaking. But any system that gives false alerts often, particularly in normal operations, will very quickly be ‘tuned out’ of the users’ consciousness. There are many examples of such systems being ignored in the minutes or seconds prior to an incident or accident. The installation of a warning system may sound like a great fix for a hazard, or a response to an incident for someone dealing with paperwork, but that system will only be of value if it truly works when needed and, of course, if the user is actually looking at it (or whatever) at the right moment or is competent to respond to the alert in an appropriate and timely manner.