Choosing parallel side or main road when route mapping

Question

When mapping routes, I often come across sections where there are roads that run parallel to each other with a block or two separating them. Often if one is a main road the other is a secondary road or if secondary then other is tertiary.

Which should I choose?

Issues: The primary is typically wider and a bit straighter, but you have more passing traffic to deal with and more vehicles entering/exiting the road. The other road though likely not as wide nor as straight, may be more scenic, has less passing & entering/exiting traffic, but you have to potentially deal with vehicles exiting driveways, which often have more blind spots than entry/exits on the primary road, plus more pedestrians and/or animals, possibly. Is it a 6, half dozen type situation, or statistically speaking one type is safer than the other?

Answer 1

This is a difficult question to answer with anything other than "It depends." but I will give my criteria for choosing between alternative routes, and then the example of my typical commuting ride.

Criteria

I can't really speak to whether one or the other choice is empirically statistically safer. However, as a vehicular cyclist, I am most concerned about any time a motor vehicle and I are going to try and occupy the same space. Where the risk is highest in my experience is at intersections and driveways. At the same time road conditions and vehicle speed can make a huge difference in ability to avoid an accident. (I've never been hit by a car in over 70,000 miles of riding, but I have crashed because of road conditions, obstacles, or poor rider decision making many times.)

When choosing between routes, when all other factors are roughly equal (distance to destination, hills vs flat, etc), I prioritize, in order:

1. Minimizing crossing and hooking encounters with cars, particularly at high speeds. So I avoid high-speed roads with lots of driveways or cross streets during peak traffic times (see my example below). It's the "intersection" and "drive-out" encounters that scare me the most. I've ridden thousands of miles on the shoulder of interstate highways with 65+ mph speed limits on weekends and early mornings and felt safer than riding in front of a shopping center or strip mall at 4:00 PM even if the speed limit is 25 mph.
2. Look for lower speed limit and lower motor vehicle traffic routes if it's likely I will need to take the lane, either for safety, or in order to make a turn.
3. Look for routes designated as bike routes, including signage and striping or other infrastructure.

Note: I actually in many cases will actively avoid designated bike routes and in particular separated bike paths because they tend to be poorly maintained, or are populated with pedestrians, skaters, and wrong-way bike riders. On-street bike lanes, when striped, tend to be in the "door-zone", and are often not any safer, or less safe even, than riding in a wide shoulder.

Real-Life Example

For almost a decade before the COVID-19 pandemic, my primary commute was a roughly 12 mile ride from a suburb of Salt Lake City, UT, to the downtown area. In my case, I would almost exclusively ride toward work in the morning on the very straight, direct and primary "State Street". This is a 3 lane each direction with central turn lane major thoroughfare that sees a ton of traffic. But in it's favor, it has HUGE shoulders for almost its entire length. So, at 5:30-5:45 AM when I would begin my commute:

• traffic was relatively light
• traffic signal priority was set in a way that at most intersections, unless a car was waiting on the cross street, I would encounter a green light
• there is very little residential property, so little overnight on-street parking
• most importantly, almost all of the businesses were closed, so there were few places where I had to worry about cars crossing my path or pulling into or out of parking lots.

That situation is entirely different at 4:00 PM when it is time to head home. So my route out of the city was usually a combination of "Main Street" or "West Temple Street", which are the two secondary streets parallel to my inbound route. Each of these streets:

• are 1-2 lanes each direction with a turn lane in-between for most of their length, and have a speed limit 10-15 mph lower than the parallel and primary State Street.
• are designated by the municipalities they cross as bike routes for at least part of each of their lengths, so there are painted lanes and share the road signs, etc.
• have more commercial/industrial zoning in places, rather than retail/commercial
• while there is more on-street parking, the traffic is lighter and lower speed, so "taking the lane" is a much more comfortable maneuver

The drawbacks of my afternoon route were:

• I encountered more stop signs and red lights, and traveled slightly out of my way. So the ride home was typically 15-20 minutes longer than the more direct ride to work.
• Much more on-street parking, so I have to watch the "door-zone", and be concerned about drive-outs. This leads me to taking the lane with some frequency.
• The primary State Street road saw much more frequent cleaning and resurfacing. So it was fast and smooth. The secondary streets tended to have more debris and road damage. The were typically "chip-sealed" every few years rather than resurfaced.

Answer 2

I would add to Gary.Ray's excellent answer the following thoughts:

• If you're entering an area on a main road and will be exiting it on the same road, it rarely makes sense to detour onto a side road for only a few blocks. Not only does this slow you down, you will be at more risk if you need to turn across traffic.
• Google Street View is your friend. If you are plotting out a route in an unknown area, get a sense of what the road looks like. It may have a great shoulder or none. It's harder to determine pavement quality, but you can get some idea of that too.
• Local knowledge also helps, even if you don't know the specific roads. There are some counties around me where I would never ride on the county roads, there are others where I would seek out the county roads. A given class of road typically has certain design standards that you can plan around.

Answer 3

I think this depends on a ton of factors.

Even if statistics would show that one type is safer than the other: I’m not sure it would apply to your individual case since a whole lot depends on the roads, time of day, day of the week, your own riding style, speed, how careful you are, how visible you are and so on.

For me personally the choice mostly depends on the length of the side road. Since changing to a side road requires you to slow down (and possibly wait at a traffic light or stop sign) it’s just not worth it for a short 200m section. This is also how some routing tools (e.g. brouter) handle it: The cost of tertiary roads is lower than that of bigger roads but taking turns also has a cost so it’s only worth it if the tertiary road is above a certain length.

Depending on the time of day, if there are traffic lights and traffic on the main road is slow, taking the side road could allow you to bypass the traffic so you are faster and safer.

Answer 4

It depends on the ride you want to do, and when you want to do it.

I've found Strava's heatmaps near cities to show a lot of use on main roads. That's probably selection bias: commuters who log with Strava are pretty keen, and may want a direct route, while the road may get too busy during rush hour to be fast. At the same busy periods people may squeeze past on the quieter roads while trying to beat the traffic. At quieter periods speeds may get a lot higher on the main road.

Conversely there are roads that I avoid as much as possible on working days, because they stay fast but get a lot more traffic, especially heavy vehicles. I'd avoid them completely, except that a couple of them are the only realistic route to the only bridge crossing a river anywhere near where I want to be. I'll ride them much more willingly at weekends.

You may want a direct quick route on a weekday, or you may want a more relaxed Sunday ride.

You may be going flat-out on aerobars training for a TT, when someone pulling out (or stepping out) in front of you is a real risk. Or you may be far more at risk from vehicles coming up behind and passing close, going slowly with a trailer. These of course are extreme examples.

Local driver culture is also a factor - that changes with the time of day/week, but also with the road. I've ridden recently through an area where the drivers are really bad for squeezing past on the main road, but courteous on the quiet roads leading to it (another unavoidable stretch of main road).

Answer 5

I suggest to concentrate on avoiding the car traffic, as collision with the car is about the most dangerous that may happen.

The only exception is if it is a pavement or marked by something like "no bicycles" or "pedestrian zone" - do not go there, of course.

Roads may have other problems, but if the one is closed for car traffic / very little used and another not, the only way how the car road could be possibly preferred is if it has clearly marked bicycle lane. Where I live, cars vs no cars most often mean also gravel or even forest road vs tarmac but be with it, I do not mind quality of the road that much.

This is, however, somewhat style-dependent. I only commute about 8 km one way so have plenty of time and can afford slow speeds no problem.

Answer 6

In addition to all of the nice answers, consider how many lanes of traffic you must cross. In the example map (which appears to be outside Anchorage, New Jersey, USA), I would travel on the main road (Ramshorn) when going north if that stretch was less than about a mile. This is because I'd need 2 left turns across oncoming traffic to enjoy the western side road.

When heading south, I would take the side roads (Frazee and River) unless I was in a low traffic hour or quite late for something. This is because right turns (where people drive on the right) usually cross no lanes of traffic and left turns on side roads are often quite safe.

Answer 7

In my experience, maps alone are not enough to make a fully informed decision. Not much relevant information was really available in maps. Street view somewhat helped, but still, some streets where not covered or had been photographed at a time of day where conditions where vastly different from what I would find when riding them myself.

During my time in the city of Lima, Perú, I commuted and worked in parcel delivery by bike. The part of the city where I spent most time had a lot of parallel choices and after riding them, I constantly got surprised how much pleasant (or much worse) the next street may be.

If I could make a generalization (that still applies to that part of the city), main streets where useful when I wanted to get to destination as fast as possible and days where I wanted a good adrenaline dose, on the other hand, secondary streets where excellent for when I needed a more relaxing ride and where I was feeling tired or with less than optimal reflexes.

Main streets require but also allow for more acceleration if you go with the rest of traffic. People are accustomed to the fast pace and somewhat "respect" the pavement. But to ride in those conditions you must be a very "aggressive" rider and be prepared to react to many, many erratic behaviors from other road users (not only in the technicalities of ridership, but in your mood reaction and mental well being)

In that sense, streets tend to hace a slower pace, less traffic and less noise. For me, that meant a more relaxed ride, as I could rely a bit more in my ears to account for rear and side approaching dangers (On a quiet street you can easily hear the rolling tires of a car, a garage door opening, etc) and also you get a little more time to react to other people's movement, since there are not as many. (takes less effort for the brain to determine where everyone is going). Yet, it was not so wise to pedal too fast, since people there are not expecting anything to move faster than a certain speed so they move without worrying too much about their surroundings.

Finally, for training, none of those options where good. The best was to go to certain spots in the city where you can ride around a park or similar. These where loops in places where traffic was really low and it was possible to ride along an uninterrupted sidewalk or curb, so it was possible to pedal "flat out" with very low probability of someone stepping in front of me or driving into my path.