I DRIVE a car that spends almost all its time on the streets of Winnipeg. Thanks to the vehicle’s trip computer, I know my average speed — 31 kilometres per hour.

So, the current debate over lowering speed limits on some city streets comes as a bit of a surprise. There is some opposition as the City of Winnipeg begins a yearlong experiment with reducing the speed limit to 30 km/h from 50 km/h on sections of four local streets. Do opponents of the move realize how fast they really travel?

The simple fact is that lowering speed limits to 30 km/h on many residential streets is not going to change how quickly you get around town — and it will save lives in the process.

It is well known that the actual speed vehicles travel in an urban area is governed by such factors as traffic volumes, the road system, accidents and construction — and not so much by posted speed limits.

A study in New York a few years ago famously found that the average travelling speed of a vehicle in Manhattan was 7.5 km/h, which means you can just about keep up to cars on foot at a brisk walking pace.

Winnipeg rarely has gridlocked traffic, but try crossing the city on Route 90 during morning or afternoon rush hours. Sure, the signs say 50 km/h, 70 km/h or even 80 km/h, but try achieving that on Wednesday at 4:30 p.m.

I am about as average a motorist as can be, driving to work and other activities over a series of residential streets, neighbourhood collector roads and highways, all within city limits. I rarely venture outside the Perimeter Highway.

Over thousands of kilometres every year, the trip computer comes up with the same average of 31 km/h in the stop-and-go traffic I encounter across the city. That’s not going to change if I have to slow down to 30 km/h on some residential streets. In fact, like most drivers, I spend very little time on residential streets and rarely drive the speed limit on them in any event. They are usually the first leg or the last leg of a journey, as they are intended to be.

The focus on speed limits shows a lack of knowledge about how fast people really drive, and also about how speed limits fit into the bigger program of road safety.

The stated goal of many cities now is to achieve “Vision Zero,” a concept that eliminates traffic fatalities entirely. Lower speed limits play a role in this. But the concept is much broader. Its goal is a safe transportation system in which the needs of street users, vehicles and the transportation network have to be addressed in an integrated manner, through a wide range of interventions.

It can involve redesigning roads, redirecting traffic, creating separate routes for pedestrians and cyclists, improved driver training and many other features. The whole system must work together and cannot have elements that are at odds with the bigger picture.