San Diego will try something new in its uphill battle to shrink emergency response times in the sprawling and increasingly congested city: roving “peak-hour” fire engines not connected to any station and deployed at busy times in busy areas. City officials say they plan to add six peak-hour engines – three in July 2019 and another three in July 2020 – to help meet a goal of having emergency crews arrive at the scene within seven and a half minutes 90% of the time. Fire Chief Brian Fennessy said this month that the city is meeting that goal about 79% to 80% of the time, predicting the peak-hour engines could significantly boost that.