Narrative:

I just relieved the previous controller; I was working normal pattern traffic and VFR ins and outs. Aircraft X called for a departure; left standard; then changed to left crosswind at river. I built a window for the departure. Ground control asked me for a crossing of 25L at lima and bravo twice. I gave the crossing at lima; and with a restriction for traffic on the runway; bravo twice. I had planned to use line up and wait (luaw) for aircraft X; but because of the tower staffing being marginal; controller in charge (controller in charge) was combined with clearance delivery (clearance delivery); and luaw was not authorized. I remembered that; so I didn't line aircraft X up. When I observed the landing aircraft clear the runway; I cleared aircraft X for takeoff; forgetting about the crossing. When aircraft X rounded the corner; the first crossing was complete. The ground controller alerted me that they were still crossing one more; and was able to stop the second aircraft Y in the flight before they crossed the hold bars. I cancelled aircraft X's takeoff clearance; they exited them from F1 and the second aircraft Y crossed without incident.I need to be more focused coming into the position. Having adequate staffing numbers for the facility to be able to use luaw throughout all busy hours would help. Realistically; most certified professional controllers (cpc) here ignore the rules of luaw for the sake of the operational efficiency.

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Original NASA ASRS Text

Title: LGB Tower Controller reported that there was approval for two aircraft to cross the runway. After one crossed the Controller reported that they cleared an aircraft for takeoff. Ground Control advised Local Control of the second aircraft that was cleared to cross. Local cancelled the takeoff clearance before the crossing aircraft crossed the hold short bars.

Narrative: I just relieved the previous controller; I was working normal pattern traffic and VFR ins and outs. Aircraft X called for a departure; left standard; then changed to left crosswind at river. I built a window for the departure. Ground Control asked me for a crossing of 25L at Lima and Bravo twice. I gave the crossing at Lima; and with a restriction for traffic on the runway; Bravo twice. I had planned to use Line Up and Wait (LUAW) for Aircraft X; but because of the tower staffing being marginal; Controller In Charge (CIC) was combined with Clearance Delivery (CD); and LUAW was not authorized. I remembered that; so I didn't line Aircraft X up. When I observed the landing aircraft clear the runway; I cleared Aircraft X for takeoff; forgetting about the crossing. When Aircraft X rounded the corner; the first crossing was complete. The ground controller alerted me that they were still crossing one more; and was able to stop the second aircraft Y in the flight before they crossed the hold bars. I cancelled Aircraft X's takeoff clearance; they exited them from F1 and the second Aircraft Y crossed without incident.I need to be more focused coming into the position. Having adequate staffing numbers for the facility to be able to use LUAW throughout all busy hours would help. Realistically; most Certified Professional Controllers (CPC) here ignore the rules of LUAW for the sake of the operational efficiency.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.