The current (2012's Measure L) half cent Sales Tax is generating close to $1 million per year. It applies to all sales in Orinda and sales outside of Orinda that can be "tied" to Orinda (such as cars which are registered in Orinda which accounts for a majority of the tax). Measure L funds are being used to repair the City's public residential streets but it is not really enogh to make significant headway. In the long range, an extension of the half cent tax can be utilized as a significant (but not sole) income source for road and storm drain maintenance.
If a sales tax tax is designated a "general" tax (not tied to a specific purpose, like roads) it only takes a simple 50% majority to pass. That is how Measure L was defined although the City Council made a non-binding pledge to use the funds for roads which the CIOC is auditing. If a sales tax is legally dedicated to a specific purpose (like roads), then a 2/3rds majority is required.
This tax is expected to increase at the rate of inflation. The Road Action Group assumes this tax will grow with inflation at 2.5%. The tax is dependent on taxable sales, mainly car sales. How this tax base varies over time is unknown as records of car sales by zip code of registration is not recorded until a tax, like Measure L, is implemented.
Sales tax is a fair (most of it comes from taxes on vehicle sales which have a nexus to roads and are generally "indexed" by wealth) and "easily" implemeted tax (it is much easier to extend an existing tax than implement a new one). It will grow with inflation which makes it applicable for long range maintenance funding. Its "weak point" is that it is of limited size so it can only be part of the solution.