The S&P 500 so far this month is lower by 1.7%. It seems like investors may still be debating the efficacy of the "sell in May and go away" strategy this year. But what is clear is that, particularly amid ongoing global trade tensions, there are good reasons to consider exchange traded funds that reside on the more conservative end of the risk spectrum.Predictably, many investors think some of the best ETFs for going conservative are fixed-income funds, but the reality is some of the best ETFs for turbulent times can span multiple asset classes, including bonds, stocks and more.Importantly, many of the best ETFs for rocky market environments also perform well over long holding periods. A variety of research points indicate the low-volatility factor delivers for long-term investors, and there are plenty of calls for the moribund value factor to regain its form.InvestorPlace - Stock Market News, Stock Advice & Trading Tips * 7 Safe Stocks to Buy for Anxious Investors Those points and more potentially bode well for some of the best ETFs for conservative investors. Here are some of those funds to consider. VanEck Vectors Municipal Allocation ETF (MAAX)Expense Ratio: 0.36% per year, or $36 on a $10,000 investment.Having debuted just last week, the VanEck Vectors Municipal Allocation ETF (NYSEAMERICAN:MAAX) is the newest fund highlighted here. Rookie status aside, MAAX is one of the best ETFs for conservative, income-hungry investors to consider. There are multiple advantages to owning municipal bonds, including steady levels of income, tax breaks and usually benign credit risk.MAAX is also one of the best ETFs for investors seeking exposure to a massive roster of municipal bonds. This new fund is an ETF of ETFs, made up of other VanEck municipal bond ETFs. MAAX currently holds four of the established VanEck municipal bond ETFs and allocates just over 70% of its weight to the VanEck Vectors High-Yield Municipal Index ETF (CBOE:HYD) and the VanEck Vectors AMT-Free Long Municipal Index ETF (CBOE:MLN).MAAX has an effective duration of 7.37 years and a yield to worst of 3.25%. Overall, this new ETF features exposure to nearly 5,900 bonds. iShares Core Conservative Allocation ETF (AOK)Expense Ratio: 0.25%The iShares Core Conservative Allocation ETF (NYSEARCA:AOK) is one of the best ETFs for prudent investors to consider and not just because "conservative" is in the fund's name. AOK is a multi-asset fund that targets the S&P Target Risk Conservative Index and uses the ETF of ETFs structure used by the aforementioned MAAX.In the case of AOK, it holds seven ETFs, all of which are other iShares funds. Currently, AOK is positioned, well, conservatively as over 70% of its weight is divided among the iShares Core Total USD Bond Market ETF (NASDAQ:IUSB) and the iShares Core International Aggregate Bond ETF (CBOE:IAGG). * 7 Stocks to Buy for Over 20% Upside Potential AOK's largest equity holding is the iShares Core S&P 500 ETF (NYSEARCA:IVV) and the fund currently features some light exposure to domestic mid- and small-cap stocks as well as some international holdings. Invesco S&P MidCap Low Volatility ETF (XMLV)Source: Shutterstock Expense Ratio: 0.25%Investors may be skittish about embracing stocks right now -- even more so when it comes to small stocks, including mid-caps. But some of the best ETFs to consider in the current environment are those dedicated to reducing volatility. Enter the Invesco S&P MidCap Low Volatility ETF (NYSEARCA:XMLV).XMLV tracks the S&P MidCap 400 Low Volatility Index, the low volatility offshoot of the widely followed S&P MidCap 400 Index."The Index is compiled, maintained and calculated by Standard & Poor's, consisting of 80 out of 400 medium-capitalization securities from the S&P MidCap 400 Index with the lowest realized volatility over the past 12 months," according to Invesco.Over 50% of XMLV's 80 holdings hail from the financial services and real estate sectors. Meanwhile, the normally docile utilities sectors commands almost 20% of the fund's weight. Cambria Trinity ETF (TRTY)Expense Ratio: 0.66%The Cambria Trinity ETF (CBOE:TRTY) is an actively managed fund that also uses the ETF of ETFs methodology. While TRTY is an active fund, it aims to replicate or beat the performance of the Cambria Trinity Index, a benchmark that "employs a balanced, systematic approach to asset allocation, focusing on diversification, value investing, and trend following," according to Cambria.Several factors make TRTY one of the best ETFs for conservative investors. For starters, its roster of 18 funds makes this one of the largest ETFs of ETFs in terms of depth. Second, TRTY offers diversification across asset classes, including domestic and foreign bonds and stocks as well as managed futures strategies. By virtue of its robust fixed-income exposure and positions in two Cambria shareholder yield ETFs, TRTY is a great ETF. * 7 High-Yield REITs to Buy (Even When the Market Tanks) The Cambria Global Momentum ETF (CBOE:GMOM) accounts for roughly a third of TRTY's weight. GMOM is rooted in momentum and trend following. Pacer Trendpilot US Large Cap ETF (PLTC)Expense Ratio: 0.6%The Pacer Trendpilot US Large Cap ETF (CBOE:PTLC) is one of the best ETFs for investors that want to automatically reduce equity exposure when markets decline. Essentially, PTLC is a rules-based strategy that uses moving averages to guide its allocations.When the S&P 500 closes above its 200-day simple moving average for five consecutive days, PTLC will be 100% invested in equities. If the index closes below that moving average for five straight days, PTLC will go to 50% stocks/50% 3-month T-bills. Five more consecutive days below that moving average and PTLC transitions to 100% T-bills.Long-term data suggest there is validity to this strategy."Over the period of 1999 through 2018, a portfolio strategy that followed a 100% position in S&P 500 when above its 200 day simple moving average or 100% T-bills when below the 200 day simple moving average produced a return of 5.36%," according to ETF Trends. "On the other hand, a 100% position in the S&P 500 regardless of market conditions produced a return of 4.86%. It can be seen that a simple trend following strategy helped investors avoid the steeper drop offs while still maintaining an investment portfolio's upside potential."Todd Shriber does not own any of the aforementioned securities. More From InvestorPlace * 4 Top American Penny Pot Stocks (Buy Before June 21) * 7 Safe Stocks to Buy for Anxious Investors * 4 Tech Stocks Looking Vulnerable * Should You Buy, Sell, Or Hold These 7 Hot IPO Stocks? Compare Brokers The post 5 Conservative ETFs for Any Market Environment appeared first on InvestorPlace.