There are many anti collision and slew restricor systems available. Below is a link to one such system but may be a bit expensive and overkill for two cranes. www.loadsystems.com/prod.../LSI_MC602_Slideshow.ppt As a construction safety manager we occasionally operate two tower cranes on some of our projects and would generally use slew restrictors. As an additional safety measure each crane operator will have two radios, one for communicating with their own slinger/signaller and one "crash" radio as we call them, on a separate channel to communicate with each other in the event of an emergency and the need to inform each other to stop immediately, such as a potntial collision. Hope this helps. (Andrew Watts)

Reneesh To take nothing away from Andrews excellent post . There are loads of Slew Restrictor Anti Zoning devices on the market. The trouble we found is people then rely on them and being electronically operated they can go wrong. We had a problem with conflicts from Concrete pumping machines as well as Taxi firm signals. As well as these systems which yes do have gliches but work. Use a robust MS and RA with a crash radio system in place as at least then you have more of a human element in place. Ta Alex