A low price per minute is useful only when calls connect correctly, sound clear, and begin billing at the proper time. Route evaluation needs both statistics and human testing.
ASR: how many attempts receive an answer
Answer Seizure Ratio divides answered calls by total attempts. It can reveal major completion differences, but it is not a pure carrier score. Busy lines, invalid numbers, unanswered calls, voicemail, list quality, calling time, and destination behavior all change the result. Compare routes using similar traffic and time periods.
ACD: how long connected calls remain active
Average Call Duration can help show whether answered calls match the intended use. A route with many extremely short calls may have audio failure, answer-supervision problems, low-quality traffic, or campaign issues. A long ACD is not automatically better; it must make sense for the business process.
PDD: how quickly the caller receives progress
Post-Dial Delay measures the wait after dialing before ringback, an announcement, or answer. Excessive delay creates a poor user experience and can encourage callers or dialers to abandon attempts. Compare the same destinations because international and mobile networks naturally vary.
Problems statistics may hide
False answer supervision can start billing while the destination is still ringing or playing a network announcement. Caller ID may disappear on selected networks. DTMF may fail even when speech sounds fine. A route may perform well off-peak and struggle during busy hours.
A practical test plan
Use valid test numbers across several networks. Include answered, busy, invalid, rejected, and deliberately unanswered calls. Confirm audio in both directions, call setup time, answer timing, caller ID, DTMF, duration, charge, and SIP response. Record the date, network, route, and result so later comparisons are meaningful.