Narrative:

Problem is intermix of high speed and low speed aircraft. Near midair collision between large transport and light aircraft while flying standard instrument departure route in contact with sac departure control. Departure control was unaware of light aircraft, yet after incident reported it would attempt to follow flight/track it to landing. Proved fruitless! Light aircraft not transponder equipped. Climbing right turn by large transport to avoid collision. Other aircraft never took any evasive action, prompting belief he never saw large transport. Other aircraft was flying southwest (200-220 degrees), 5500'. F/east first spotted other aircraft, followed by copilot, then captain (flying at the time). I firmly believe a midair collision would have occurred were it not for alertness and good scanning technique of the F/east. A collision avoidance system is long overdue. The incongruity of it all is getting traffic reports at cruise altitude (where it is not needed or necessary) and not getting them at the lower altitudes (less than 10000') where the problems exist.

Related reports:

Google
 

Original NASA ASRS Text

Title: CLOSE PROX ACR-LGT GA-SMA ABOVE MCC ARSA.

Narrative: PROB IS INTERMIX OF HIGH SPD AND LOW SPD ACFT. NMAC BTWN LGT AND LIGHT ACFT WHILE FLYING STANDARD INSTRUMENT DEP ROUTE IN CONTACT WITH SAC DEP CTL. DEP CTL WAS UNAWARE OF LIGHT ACFT, YET AFTER INCIDENT RPTED IT WOULD ATTEMPT TO FOLLOW FLT/TRACK IT TO LNDG. PROVED FRUITLESS! LIGHT ACFT NOT TRANSPONDER EQUIPPED. CLBING RIGHT TURN BY LGT TO AVOID COLLISION. OTHER ACFT NEVER TOOK ANY EVASIVE ACTION, PROMPTING BELIEF HE NEVER SAW LGT. OTHER ACFT WAS FLYING SW (200-220 DEGS), 5500'. F/E FIRST SPOTTED OTHER ACFT, FOLLOWED BY COPLT, THEN CAPT (FLYING AT THE TIME). I FIRMLY BELIEVE A MIDAIR COLLISION WOULD HAVE OCCURRED WERE IT NOT FOR ALERTNESS AND GOOD SCANNING TECHNIQUE OF THE F/E. A COLLISION AVOIDANCE SYS IS LONG OVERDUE. THE INCONGRUITY OF IT ALL IS GETTING TFC RPTS AT CRUISE ALT (WHERE IT IS NOT NEEDED OR NECESSARY) AND NOT GETTING THEM AT THE LOWER ALTS (LESS THAN 10000') WHERE THE PROBS EXIST.

Data retrieved from NASA's ASRS site as of August 2007 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.