Air Traffic Control Fully Certified
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance
Procedure
Aircraft X was cleared for takeoff on Runway 19R. They self cancelled; and exited the runway. I returned them to the end; and told them to expect a few minutes for departure due to traffic on the intersecting runways. The Controller working those runways then called to give me the intersection earlier than I expected. He had an aircraft departing 25R; and I got control of the intersection after that. I had an aircraft on final for 19R; about 3 miles out. I asked Aircraft X if they could take it on the roll; and got an affirmative. I then told them position and hold; don't plan on stopping; to get them out in front of the lander. I issued traffic to both the lander and Aircraft X; and cleared the Aircraft X for takeoff as soon as the departure traffic passed through the intersection; and I had control of it. All of this worked as planned; and would have been fine a short time ago. However; with the 'virtual intersection' rules now in effect; I forgot to use those; and had traffic landing the virtually intersecting Runway 25L that was about a half mile from the inner edge of the go/no go box. This was Aircraft Y; landing 25L. They landed without incident; and there were no proximity problems; however I did not properly apply the rules; and had a procedural error. Had I waited 3 or 4 more seconds; I would have still been able to depart in front of the lander; but would have been legal. After 20 years of not having to think about the landers to the non-intersecting runway; other than if they were going around; I simply forgot the new rule.On my part; do not try to push the traffic out quite so quickly. If I had waited; it still would have worked. We were not in delays; and no one had been waiting long. I relied on my past experience; which usually works great; but not in a case where the rules have changed. I rushed; and had an undesired result. I would recommend that we have a phase-in period for major changes like this; however. In the past; when there has been a rule change that was totally opposite of what we were used to; we were given a 30 or 60 day window where the rule was in effect; but if you used the old procedure; they considered it a learning experience; and reminded you that we had new rules. If this was the case; I would have just had one of those learning experiences.
Controller reports loss of separation  due to 'Virtual Intersection' rules that were not executed correctly.