A nationwide test of the four major US carriers' cellular networks puts Verizon Wireless and AT&T in a near-tie in most categories, with Sprint and T-Mobile lagging well behind their bigger rivals.

Verizon was the winner in four out of five categories, including reliability, data, calls, and texts. AT&T won the speed test by a hair and finished slightly behind Verizon in the overall score.

Test results for the second half of 2013 were revealed today by RootMetrics, which calls itself an independent mobile analytics firm. The tests don't appear to be funded directly by any of the carriers, but RootMetrics' business sells "subscription data products to strategic wireless carriers, infrastructure companies, and device manufacturers."

RootMetrics said it "drove nearly 220,000 miles, visited 6,300 indoor locations, and collected more than 4.6 million test samples" in order to collect its data. Android-based devices were used for all tests, which the company performs twice per year "in the 125 most populous metropolitan markets across the United States" as well as the 50 busiest airports. In addition to the top markets, test locations are randomly selected in each state. Results are weighted by population size.

The RootMetrics results are presented on a scale of 1 to 100 rather than in megabits per second, signal strength, or other specific metrics.

The reliability index includes results from data, calls, and text tests, while the speed index includes results from data and text testing.

Verizon's overall ranking (including speed, reliability, data, calls, and texts) was 89.7, ahead of AT&T's 86.2. Sprint and T-Mobile scored 68.2 and 64.3 percent respectively. RootMetrics also published scores for each state, where results tend to vary. AT&T led the pack in Massachusetts, for example.

The 1-100 scores don't really tell us much about real-world performance, though Verizon trumpeted the results, saying the "report confirms we are meeting and exceeding our throughput brand promise of 5 to 12 Mbps on the downlink and 2 to 5 Mbps on the uplink across our footprint." Verizon today also talked up plans to bolster its cellular network and begin routing phone calls over LTE this year, according to Re/code.

More useful for individuals are RootMetrics' smartphone apps for iPhone and Android. Consumers can use them to test their own devices' performance and compare it to the general performance in their geographic region.

When testing my Verizon Wireless connection at my home in suburban Massachusetts, I got the following results:

Average test results in my area showed Verizon pushing less than 1Mbps on both download and upload:

In this small sample, MetroPCS scored greater than 1Mbps in download, but only 150 to 249Kbps in upload.

RootMetrics tests call performance by "plac[ing] a call from each network’s phone and attempt[ing] to hold that call open for the duration of the test cycle. Our testing shows blocked call, dropped call, and overall (blocked and dropped) call failure rates." Texting is tested via "failure rates and the speed at which each network can receive a text from 1) a phone within its own network and 2) phones from other networks."

For data transfers, RootMetrics tests file uploads and downloads to approximate typical activity like downloading e-mail and apps or loading webpages. "During file transfer testing, RootMetrics attempts to open an HTTP connection(s), and then measures network connection success rates, as well as upload and download transfer speeds," the company said. "To represent the consumer experience of loading apps or webpages and checking e-mail with a smartphone, our testing measures how reliably and quickly each network is able to: 1) connect to an IMAP server and download a group of 10 e-mails and 2) establish a data connection and download lite data files that represent typical Web and app behaviors."