Manteca leaders are aiming for a “D” when it comes to traffic everywhere in the city except downtown.

In downtown, they are content to settle for “E” or – when traffic is heaviest – “F” levels.

Targeted  traffic standards are contained in the Manteca general plan. The document is used as a blueprint for growth.

The letter grades of “A” to “F” for levels of service devised by traffic engineers weren’t designed to mirror school letter grades.  Instead they are assigned to reflect desired traffic flows with “A” being optimum and “F” being the least effective movements.

Streets rated as “A” level would never have more than one car at any time at a stop sign. Traffic would flow through signalized intersections as if it were always 3 o’clock in the morning.

By adopting “D,” Manteca leaders downgraded a previous stated goal of “C” level service. They did so in a move to save money, enhance safety,  and to slightly de-emphasis vehicle dominance in neighborhoods and elsewhere in Manteca.

The level “C”  describes at or near free-flow operations. Roads are close to capacity in terms of traffic volume while  posted speeds are maintained.  It is the same level of service Caltrans targets for some urban freeways and most rural highways.

By dropping down to “D” level, the city is accepting that speeds will decrease slightly when traffic volume decreases slightly. Cars typically are about eight-car lengths apart expect during peak hours. That compares to 11-car lengths for level  “C” service.

 It means future streets won’t be as wide. It also means bicycle lanes sharing more streets as well as traffic calming near intersections to slow traffic down and to provide greater safety for pedestrians crossing the street.

Manteca’s previous goal of “C” level streets would have had major impacts in costs and the quality of life in the community if it were retained and actually implemented to the fullest as growth occurs. It would have required additional lanes by taking private property and likely require the demolition of houses and other  buildings. It could also have required the city to build bypass roads which given how the city is laid out would have meant massive condemnation of property to accomplish.

While  Manteca is pursuing “D” level service elsewhere, it is not in the downtown district . That’s because traffic is so heavy at times downtown that to accomplish a “D” level it would entail adding extra travel lanes. That, in turn, would require taking out businesses on one side or the other of both Yosemite Avenue and Main Street.

The downtown district for traffic purposes is defined as Walnut Avenue on the west, Powers Avenue on the east, a block south of Yosemite west of the railroad tracks and Moffat Boulevard  on the south and well as North Street to the north. The only exception is Main Street where the northern boundary of downtown is Alameda Street.

For new development, keeping “C” level as a goal would have required wider streets with more lanes. That in turn would encourage higher speeds and make major streets – and even collector streets – less inviting for pedestrians and bicyclists. Such streets could also have added $10,000-plus to the cost of a typical home beyond the growth-related road fees that are currently in place or are expected to be assessed to achieve traffic service levels rated as “D.”