The example with the House of Representatives has nothing to do with roads, but the concept of arbitrary caps does. In this case, it is the mileage cap used by states to limit highway system expansion to a set mileage. The mileage cap is essentially a state agency deciding that they will no longer accept any new miles into the state highway system regardless of overall gains in road mileage. Usually when these caps are created, it is done as a hasty action as a means to stop the bleeding of funds for a road system that was growing past the point of efficiency or as a means to reign in politically motivated roadways that never had any reason to be on the highway system and were not otherwise part of a special farm-to-market highway network. Mileage caps are typically based on a completely arbitrary number that is set that essentially rounds off what just happened to be the approximate state highway system mileage at the time usually rounded off. The result, however, has been hardship for local governments and leads to the slow, but proportional devolution of the state highway system.
Why is this bad? These states with such caps use the "lane miles" argument to justify a continued devolution of the highway system, but evidence in these states is that the local funding ratio likewise does not increase in relation to the proportional decrease in state responsibility. Lane miles will almost always increase regardless of who is in charge, and the "lane miles" argument is a weak one since population and thus the state's tax base also increases in conjunction with added lane miles. If the state doesn't want more lane miles, then they can always choose to build, widen or pave fewer roads focusing funding instead on operational improvements. This Trojan Horse argument has nothing to do with the unfunded mandate known as the mileage cap. In addition, far more miles go to the local governments than the mileage indicates. This is because every time a new road is built and added to the state highway system, some road must be downloaded to the local government, especially when a roadway is entirely new construction instead of a relocation of an existing highway.
Local governments are still largely dependent on state funding, and local governments are generally not the most efficient means of maintaining arterial and major collector roads. This was detailed in the Farm-To-Market Cooperative Plan. When the state sets a mileage cap, it does not just mean that an old highway alignment is placed on the local level when a new road opens. It also means that other highways, usually in rural areas, are also turned to local maintenance. With no additional funding or state maintenance, roads like this tend to fall into disrepair under local control. This is especially true when local policies and practices for road maintenance are already weak meaning that these local agencies are not going to make any special effort to maintain a former state highway vs. other local roads. The need to "swap" roads simply leaves local governments with the cost of maintaining a road that they never built in the first place that they likely also lack sufficient means to maintain. In all, it is a bad transportation policy and it weakens the abilities of local governments to manage limited funds by spreading available local funding even thinner.
What's also worse with mileage caps is that it prevents the road system from periodically being corrected to better adapt to new traffic patterns. Roadways that no longer serve any statewide purpose are kept on the state system because the local agency does not want to lose those miles just to gain more on another road. The states also start using these roads as "mileage banks" to withdraw at random just to deposit as added mileage for another new road meaning that the state has already deemed these older routes effectively useless. Often times, a "lane mile" swap is even required thus a local agency is stuck with maintaining sections of roads twice as long as the new state routes. Because of this, local agencies rarely propose any changes that would make sure that state routes actually line up with the best and most useful function. If local agencies were not always threatened with losing state highway miles, this attitude would change and better routes would thus be developed.
The ratio cap is a concept that balances the needs of the state with the needs of local governments. If a local agency's road responsibility massively increases then likewise they should be seeing more roads turned to state control. They shouldn't have to worry if it "meets state standards" or that they have to "swap out another road". In fact, all counties and municipalities should be able to put out a wish list each year on qualifying roads to place onto the system with the state able to add them based on the greatest need. The state then takes them over as-is and then makes the needed changes themselves. Picture this example in "sample state".
- Sample State created a mileage cap in 1980 that restricted the state highway system to 10,000 miles
- In 1980, the sum of all public roads in the state was 80,000 miles
- Since 1980, the public road system has grown since then by 20,000 miles to 100,000 miles
- In 1980 the state ratio was 12.5% under state control
- In 2010, it had since dropped to 10%
- The state also built and took over maintenance of 2,000 miles of new roads thus transferring 2,000 miles of other roads from the state system to the local system
- This means that local agencies have had to take on an additional 20,000 miles of roadways without any additional funding from the state to do so
- This 20,000 mile mandate includes 2,000 miles of roads formerly maintained by the state
- Seeing that the state ratio in 1980 was 12.5% when the cap was created, the state agreed to expand the state highway system back to the ratio it was in 1980
- The state will continue to maintain this ratio cap not exceeding 12.5%, but it will allow the road system to grow thereafter in proportion to total system growth
- This means that 2,500 miles will now be added to the state highway system
- 1,500 of the 2,000 miles turned to the local authorities are then restored to the state highway system since they were determined to remain of high enough functional classification and traffic volumes to justify restoring
- 1,000 miles of new state roads along existing local roads are added with mileage shared evenly among all 10 state highway divisions so that each division is able to add 100 miles of local roadways to the state system
- Many local agencies were then no longer torn between paving and upgrading miles of former state routes and other major local roads
- In 2015, the public road system grew an additional 500 miles
- Thus, the state allowed up to 63 more miles of roads to be added to the state highway system since 2010. 50 of those miles were new roads with a couple old alignments retained as business routes. 13 additional miles were distributed to all 10 districts with some used and some reserved for additional growth of the system.
- While the state's responsibility increased, proportionally it did not change from 1980 after the mileage cap was replaced with a ratio cap and the 1980 ratio restored.
It is understood that one of the reasons for mileage caps is to force counties to take over segments of old alignments that they would refuse to give up otherwise. In states like Louisiana, Mississippi and Maryland it is not uncommon to see dead end roads, including old alignments with long-closed bridges, remaining on the state system. However, this is a mileage distribution issue not a road mileage issue: it is a management issue. The state DOT should have the authority to say "this road is not necessary for statewide travel and will be returned to the local government" while transferring that mileage to a road that does serve statewide traffic. It is ridiculous to see roads that obviously serve a statewide purpose as county roads so that a road that no longer serves any purpose except as a two-lane driveway remaining on-system. You see this sometimes in Maryland where a state primary route in Pennsylvania becomes a county road in Maryland while five sections of an old alignment nearby are still state highways. Assuming that the county road has equivalent mileage to those segments, does it not make sense for the mileage to be transferred?
- Louisiana has instated a mileage cap with a net gain of only 12 miles
- Pennsylvania has lost 4,629 miles in those 20 years (the system began scaling back mileage beginning with a large-scale turnback event in 1984)
- South Carolina instated a mileage cap in 1993 but has officially turned back 245 miles
- Kansas's state road mileage dropped by 356 miles despite a gain in local road mileage of 6,959 miles.