Home > PA State Routes > Numbering System

The Pennsylvania State Route Numbering System

Your guide to the methodology behind the numbers assigned to state routes, past and present.

Introduction

The latest Official Transportation Map from the Pennsylvania Department of Transportation (PENNDOT) shows, at first glance, a random scattering of numbers across the state. No clear pattern appears that suggests that the state route numbers were chosen by some methodical or systematic set of rules. Yet one familiar with the Interstate and US highway systems knows that these types of highways had fairly strict numbering rules. For example, I-80 and I-76 are east-west highways because they are even numbers, and I-80 is north of I-76 because higher numbers were given to highways further north. A similar system is intact for the US highway system, composed of routes like US 20 and US 40. These two particular routes also run east to west because the numbers are even, and US 20 is farther north than US 40 because the higher numbers were given to routes further south. These types of routes, just like the Pennsylvania state routes, are distinguished by their characteristic route marker shields, which today look like the following:

80
22
45
Interstate
Highway
United States
Highway
Pennsylvania
State Highway

But the state routes, which are often shown on maps with the numbers circled or boxed, appear to be have randomly assigned numbers, not at all like the Interstate and US highway system numbers. A closer look at the map reveals a few local patterns. For example, there are a few clusters of routes that share the same last two digits. In the north-central part of the state near the New York border, several x46 routes appear: 46, 146, 246, 346, 446, 546, and 646. One might also notice, for example, that many odd-numbered routes that end in 1 appear in the southern part of the state, while many that end in 9 appear in the northern part of the state.

The reality is that the numbers assigned to today's state routes are the results of a mix of numbering systems, starting in the mid-to-late-1920s with a very methodical and well-planned system that established most of the route numbers seen today and most of those that disappeared long ago. With the additions of the US and Interstate highway systems, whose numbers took precedence over their concurrent state routes numbers, the renumbering of some state routes occurred to avoid duplicated numbers between the systems. For example, a numbering rule reassigned the number 192 to PA 95 when I-95 was built and designated starting in the 1950s. In later decades, many seemingly random numbers were assigned to new and existing routes, erasing many of the earlier patterns in route numbers. The result can be seen on any recent or current map: a smattering of numbers, many logical and many not.

The following pages about the Pennsylvania State Route Numbering System are divided into two parts. Part I begins by discussing pre-1928 numbering systems, which were wholly or partially abandoned upon the advent of the US highway system. Part I continues by describing in detail the system of parent, child, and spur routes that comprise the modern numbering scheme, which has been abandoned, and how the US and Interstate highway systems affected route numbering. Part II is a reference section that lists state routes assigned since 1928, showing how they fit or did not fit into the state route numbering system. This second part also includes a list of route numbers that were never assigned.

Begin with the Early Numbering Systems >>
Or browse the following Table of Contents:

 

The Pennsylvania State Route Numbering System · Table of Contents

I. Numbering Systems

II. The 960 Pennsylvania Highways

Sources and Links

Other Highway Numbering Web Sites

 

 


Back to PA State Routes
Central PA/MD Roads